Use a glowstick in front of the door on the first level after "loading" is complete.

Find remnants to spawn the sigil in the sigil room. Take the sigil (bear/doll/etc) from the sigil room to the locked door. Rinse and repeat.

Enter records room. Note switch behind desk Progress deeper into the records room. Move a box and climb it. Turn on the power. Switch is now active.

You will now be in a new maze that looks like the one you just went through. ("Hospital 2") If you encounter multiple staircases- explore what's above and below them first. Odds are good that the top or bottom of a staircase will be a dead end.

Witches can now harm you.

Past the locked door is Mercer's office. Use lamp on desk to open secret passage.

Turn on power to switch, flip switch.

Turn on power to bridge controls, activate bridge.

Turn valve to spill gas on docks, ignite gas with flare.

There's a box of flares at the top of a hill in the middle of the forest.

In construction yard avoid falling into black goo.

Walk forward.

Getting lost? Keep making right or left turns to explore entire maze methodically.

Witch? Avert eyes.

I realize this guide is very "bare bones", please post any confusions or suggestions in comments!