In this walkthrough I describe only story-related route and checkpoints, so you still have to search for ammo and medkits by yourself. The thing is, for most of the time to progress further you can use in-game "Clues", but sometimes there is no help from them (i.e. characters talk about their ideas instead of mentioning where should they go next). On my first playgrought I stucked heavily every time that happened, and that motivated me to wrote this walkthrough.

If you are a novice in survival horror genre, or if you like modern-style walking simulator/ exploration games without too much of a challenge, I recommend you to start your first playgrought with an "invincibility" cheat code - Desolate City is a fairly hard game even on "Easy" difficulty, so, to avoid frustration of loosing all the progress between the checkpoints because of unpredictable death, you may like to learn the combat basics and the maps first. On the other hand, with cheat codes you won't get the "A+ Rating" that is required for activation of additional mini-campaign after the credits. Yet, you still can play it right from the main menu using "The Gray Soldier" cheat code and hitting the "New Game" button, so it's up to you to decide if you are truly prepared for a hardcore survival horror gameplay.

Part 1: From Start Room to Archives Hidden Room

1) After the intro cutscene, walk out of the Start Room using the stairs. In the theather hall, go up - there you will find a Pipe, the first weapon in the game.
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2) Go right, take the Archive key in the last room on the upper-right (a door that leads behind the scene). Nearby, in a room on the left, you can find a note.
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3) Go back to hall, then go to the left and open the door to Archive.
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4) Go to upper-left room of the Archive and interact with a chimney in there. Unlike other chimneys on location, there is no fire in it, but it hides a secret room with the stairs to the Basement.

Part 2: Theater Basement

5) In the basement, go to the first turn on the right - there is a checkpoint (together with pistol ammo).
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6) Go back, then go down - in the end of the corridor there lies a corpse with the Pistol Room key. Be prepared to run from the enemies that will appear from the upper part of the screen - go to the nearest turn on the right.
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7) Go through the long corridor to right, in the next room continue to go right. In a room with maniac Policeman and a door with the word "Treasure" on the wall (remember it, but don't enter for now - it's a deathtrap before the power won't be restored). Go down - the Pistol Room is there. Take the gun, read the note, exit the room.
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8) Go right, then up - here's the stairs to the previously blocked part of the first floor of the theater.
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9) Go up - you will find the Basement Watcher Office key (that is situated in Start Room) near the closed door. Go back to the basement.
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10) Go down, then left, then up (in a cross-shaped corridor). On a crossroad, go up and unlock the door, then go down and unlock the other door. Enter it. In a new room, go up the stairs to the right.
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11) You are in a theatre hall again - go right, to the Start Room.
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12) In the Start Room, open the door on the upper wall. In a new room, take the Power Room key and make all the way back to the cross-shaped corridor in the basement.
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13) Go up, then right, then down on the first turn. Don't try to go up the stairs (with the word "Treasure" on the wall) if you want to continue the game, that's a deathtrap. On the other hand, you will get a Steam achievement if you will do so (don't forget to save on a nearby checkpoint).
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14) Go down and open the Power room. Beware of the maniac Priest (its better to deal with him with a pistol). Go left, take the 2nd Floor Acces key from the table. Use the panel with buttons on the wall to restore the power supply.
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15) Return to the cross-shaped corridor, go to the right. It's time to enter the room with the word "Treasure" on the wall. Beware of the enemies, go up and right, and to the small room in the end (see the map). Take the Courtyard key, beware of the new enemies, run away from "Treasure" room.
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16) Go right, then up, then on the stairs - to the previously blocked part of the first floor of the theater (where you found the Basement Watcher Office key). Open the door to the upper part of the theater.

Part 3: Two Floors and a Dead End

17) Go to the upper part of the screen, then four doors to the left (enter the fourth room counting from right to left). There is a checkpoint in there. Exit the room. Optionally: If you want to speedrun the game, see note 26) of this walkthrough - you can ignore all the optional activities, but in that case you will find less resources.
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18) Go to the door on the right (third door), take the Computer Department key that lies near the table on the right side of the stage. Exit the room.
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19) Go left, to the stairs to the second floor. After the cutscene with helicopter, go down, then right. On the bottom part of the screen there are three doors (see the map) - door on the left leads to the toilet with a note, the middle door is closed and the right door leads to Computer Department (go there).
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20) Take "Hall 1" key (and an ammo for pistol). Optinal: Interact with the papers on a table - you will find a password that protagonist may use on a computer in a Start Room to gain more information on a lore (and a Steam achievement). You don't have to remember it because the game never asks you to enter it - you need to activate the in-game script in this room and then went back to Start Room computer. Exit the room and go all the way back to the stairs to the first floor.
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21) On the first floor, enter the door you see in the upper part of the screen (the fifth door in the room, on the left from the checkpoint room).
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22) Take the key to "Undefined Room" from the stage. Now go all the way back to the second floor, to the screen with three doors (one of which led to Computer Department).
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23) Go through the middle door. Go down through fake "black walls", take the resources and a key from Screenwriting Department.
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24) Go back to the stairs on the first floor, but don't descent. Go to the corridor on the right. Enter the only available door at the end of the corridor.
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25) A-a-and here comes the dead end! This room contains a checkpoint, but no additional key that can give a hint where to go next! And it's a super-confusing gamedesign decision, because all you have to do now is to wander around the whole building searching for any hint (that's one of the cases where the "Clue" option doesn't work, because our character talks about the helicopter that have nothing with your further actions).
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26) Surprisingly, to continue the walkthrough you have to go back to the screen with three doors, and then to go right - to the corridor that leads up. You will find a stairs to the first floor - don't use it. Instead go left, and at the end of the corridor you will find the key to "Hall 3".
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27) Go back to the nearest stairs to the first floor. Go down. Enter the door you see in the upper part of the screen.
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28) Take the Business Corridor key from the scene, exit the room and... backtrack all the way to the place where you found the previous key! It means, go to the stairs on the right, then, on the second floor, go left to the end of the corridor and enter the door. Watch the cutscene.

Part 4: Three Bathrooms and Magna Room

29) As a male character, take Katana and a key to the Corridor to Magna Hall. There is no map to this little episode. Exit the room.
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30) Back to female protagonist. Optional: enter the first door on the left in the upper part of the screen to participate in an optional boss fight with James W.T. III; you will get the achievement in case of winning. Go right, this will start the lenghty cutscene with lots of dialogues.
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31) We are in that familiar corridor again. But now we have a key to the Corridor to Magna Hall, so go back to familiar room with three doors on the lower part of the screen. Enter the door in the upper part of the screen.
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32) Go up, enter the room with a checkpoint and a key to enigmatic "Bathroom". There are three bathrooms in the building, but we need to start from the closest ones.
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33) Go back to the room with three doors, then go back to the first floor using the stairs (no matter which side of the second floor labyrinth you will choose to get there). Enter the door to the checkpoint room (fourth door on the upper part of the screen if counting from right to left).
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34) In there, enter the door in the upper part of the screen.
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35) Take Another Bathroom Key lying on the left side of the screen (its shining is barely seen on the white background) and a pistol ammo. Which bathroom do we need to inspect next?
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36) Of course that one Bathroom near the Start Room! Because backtracking is always so very fun! Exit the checkpoint room. Take a few steps to the right. On the lower part of the screen there is a door to the Courtyard (check the map), enter it.
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37) Run down the road and enter the door at the end of it (the enemies may pursue you). We're in a theater hall now, near the Start Room.
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38) Go right and enter the Bathroom door on the walls in the lower part of the screen.
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39) Take Yet Another Bathroom Key. Yup, the third one. Now you have to go all the way back to the hall with five doors. You can go the same way as you came, through the Courtyard, or you can use the secret passage from the basement: previously stairs from the room with word "Treasure" on the walls led to a deathtrap, but now it leads to the mentioned hall.
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40) In the hall, enter the second door (counting from right to left).
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41) Enter the bathroom door on the upper part of the screen.
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42) Take the Magna Hall key near the toilet. Exit the room, watch the cutscene.
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43) After the cutscene you have to go to the second floor room with three doors at the lower part of the screen (and enter the door at the upper part of the screen).
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44) Go up through the corridor to the checkpoint room, enter the massive door (the game will mention that you may want to save the game). Watch the cutscene.
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45) In a new room, go down the ladder. Go right, watch the cutscene.

Part 1: Sewers

46) We got a new protagonist, but there is no way to access the map in a sewers. Go right.
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47) On the first branching path, go right.
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48) Continue to go right, then down. On the second branching path, go left.
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49) Go up through the corridor and you will come to the room with a sewage river. Here you can see how a shiny object is swimming away down the screen.
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50) The most counterintuitive thing in this scene is the realization that to get the shiny thing you need to go up. Go back to the second branching path, take the way up.
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51) Go back to the first branching path and take the way up again.
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52) On the third branching path, you may first go to the right (climp up the ladder to find the resources), but the shiny object is in the room to the left.
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53) Take the shiny object, go back to the first branching path, go right. On the second branching path also go right. Climb up the ladder.
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54) Whoa, we're in a checkpoint room inside of a church! Enter the door at the upper part of the screen.

Part 2: The Great Key Hunt

55) As it appears, the shiny object that was swimming in a sewage is a keys from the church door. How convinient! Be prepared to kill a Priest maniac that you will face just after the enter - you will visit this room many times because it holds two parts of a "church" location together (the first floor and the second floor).
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56) Go right. Be prepared to run through the Priest maniac (because for now, using Katana only, it's dangerous to fight them too often - they got more HP and attack power than regular enemies).
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57) Take the unidentified key from tabernacle (yellow box) under the stained-glass window.
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58) Go down to the lower part of the screen, then go left. Read the note on the table.
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59) Go back to the room between two floors and head up (to the second floor).
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60) In the next room, go right. Watch the cutscene.
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61) In the next room there are three doors at the upper part of the screen, one door at the lower part, and a maniac Priest in the middle (it's better to liquidate him, because you will visit this room often).
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62) Enter the left door, prepare to run away from the female maniac, take the Dining Room key, exit the room. Optional: if you want to get the shotgun as fast as you can, see notes 70)-73) of this walkthrough; I don't recommend to do it, because it's better to save ammo for Act III, and because technically it's not too hard to finish Act II without a single shot).
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63) Go right, enter the left door on the upper part of the screen, run away from the Priest
maniac and take the unidentified key from the table. Exit the room.
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64) Go right, run away from another maniac Priest, enter the door at the lower part of the screen.
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65) There are two Priest maniacs and another unidentified key on the table on the lower part of the room. Take it and run to the exit.
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66) Go right. Optional: Enter the door at the upper part of the screen to trigger an optional boss battle. Watch the cutscene with the Nemesis-like monster bursting from the wall. You can fight it (it will be exhausted after a dozen of hits by Katana and you will win the battle) or simply exit the room (it will not follow you; the mentioned battle is optional and, frankly, completely useless for a progress; it's very hard but you won't even get the achievement if you'll win).
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67) Go down - there is a corpse with a shiny object lying nearby. It's a key to the Boiler Room.
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68) Go to the room on the right from the corpse - it's a checkpoint room. Interact with the woman's corpse in a lower-right part of the screen (that is hidden with plant's leafs) to get another unidentified key.
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69) Go back to the room with three doors on the second floor. Enter the middle room. Watch the cutscene. A woman named Daphnie needs clothes to run away from the church. You have no need to inspect wardrobes you see in a different rooms, because they are hidden in the middle wardrobe of the room you will visit later on your walkthrough.

Part 3: Getting the Shotgun and Solving Daphnie's Problem

70) Go back to the room between floors. Enter the first door at the lower part of the screen. Beware of two Priest maniacs (it's safer to run away from there).
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71) At the lower part of the room there is a Library [Shotgun Room] key in a plant pot. The doors on the lower part of the room are closed, so run away to the exit at the upper part of the room.
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72) Go right, then go down - come back to the place with the note on the table. Go left and in the next room enter the large door on the right - it leads to Library [Shotgun Room].
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73) Take the shotgun. Don't forget to press the X button on the keyboard to reload it. Go up and take the Office B Door key. Also, you can interact with the door at the upper part of the screen to open a shortcut to the room where you found Library key, but if you did not killed the enemies, it's not much of a use (it's better to save shotgun ammo for now).
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74) It's up to you to decide what to do next. You can exit the room through the door at the lower part of the screen. Then you can enter the left door - the Boiler room with a hole in the floor that will transport you to the sewers without ability to turn back. Or you can find clothes for Daphnie to help her escape.
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75) For the sake of completeness (and narrative, because this longer route is crucial for understanding the plot of the game), let's help Daphnie. Go to the second floor and enter the door to the left from the stained-glass window.
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76) Beware of two Priest maniacs (or deal with them using shotgun, but remember that you will need ammo in future). Take the Sacristy key from the table.
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77) Go back to the room between the floors and enter the door at the upper part of the corridor.
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78) Take the shotgun shells, inspect every of three wardrobes in the room. The middle one will trigger a cutscene (thad sheds light on a past of one of the main characters). After the cutscene, inspect the middle wardrobe for the second time to successfully find clothes for Daphnie.
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79) Go back to the second floor to Daphnie's room. Enter it if you want to trigger the optional boss battle (because Daphnie is a maniac too now). As a prize, you can take shotgun shells from the corpse lying on the floor.
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80) Go the Boiler room on the first floor. Jump down the hole in the floor.

Part 1: Sewers and the City

81) It's sewers again, and - again! - there is no map for the place. Go left, then down. Turn left in the corridor that leads down to find a hidden room with resources.
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82) Continue to go down. There will be a place with three corpses that make a path to the right - agree to jump on them to gain access to an optional boss battle (the hardest one in the game). It seems like this battle is not achieveable with "invulnerability" cheat code, because when I used it to write a walkthrough after the first playgrought, there were no swimming corpses to jump on them; thanks to YouTube channel "adricarra" for the source of the picture on the right.
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83) If you don't want to participate in optional boss battle, go left and continue to the end of the corridor. Climb up the ladder.
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84) Now you're in a subway station. The map is still unavailable.
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85) Go right to find resources, then go left. When the monster will appear, run back to the previous screen, then go left again - the monster will vanish. Go up.
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86) On a branching path, go right to find a checkpoint room, go left to find resources and go up to walk out of a subway to the city.
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87) While the City is huge, there are only three active spots you need to interact with to progress with the plot. The other parts of this area contain enters to other subway stations where you can find checkpoints and resources for the final boss battle, so it's better to check the whole location to obtain more ammo. If you already have full clip of shotgun shells and if you're not planning to spend them on maniacs (because you are skilled enough to run away from them), you can go straight to the story-related zones.
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88) At first, just after you get out of the subway, go right (running through the maniacs) until you'll find a checkpoint zone near the car.
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89) Interact with the car from the front - protagonist mentions that the car needs Battery and a Gas Can.
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90) Go to the Central Area (according to the map), and enter the station that is called "Central Station" (don't confuse it with "Police Station", it's on the right from "Central").
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91) Go up. Enter the left route to get to checkpoint room. After that, enter the left vertical route, go to the end of the corridor. On the platform, take Battery, and go back to the city. Expect the cutscene with the monster; on the other hand it's harmless for now.
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92) After that you need to get to Industrial Park (according to the map). There is a place with a tree and a shining object that you can find near one of the stations. Interact with this object - it's a Gas Can with fuel. Yup. Like that. In a misty night city. With no in-game clues. It took me almost a hour to find it on a first playgrought.

Part 2: Last Battle and Escape

93) There are two more interesting active spots on the map that can give information about the plot of the game. The first is Theater's Entrance that is easy to find because of the map. Interaction with the gates triggers the cutscene about the past and the present state of one of the main characters.
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94) The second interesting active spot is near the Theater Gates. After you saw the cutscene, go right. On the next screen go up. Then go through the unobvious route that hidden in upper-right part of the map to get to the basketball field - there is a hidden notes in upper-right corner of the field.
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95) Go back to the car. Save on a checkpoint. Interact with the car from the front. After the cutscene, go left. After the second cutscene, the final boss battle will start.
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96) Remember enemy's patterns of movement and attack, shoot it with rifle, and sooner or later it will be defeated. Take the shiny object that the boss left - it's the car keys.
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97) Watch the final credits. If your rank is A+, after the credits additional mini-campaign "The Gray Soldier" will launch. If your rank is lower than that, you can start this mini-campaign via cheat code.

98) This mini-campaign is truly "mini": all you need to do is to run through the enemies even without fighting, no matter which route will you choose - both branches have ladders that lead to the same room on the second floor. Then you have to run through one more corridor and climb one more ladder at the end of it. The path to exit is more or less narrow. If the enemies surrounded the new protagonist, use his super-power on X keyboard button (super-power meter fills up when the character is attacked).