Speak to Klara at the entrance to the cells. She’s trying to treat the prisoners and the guards won’t let her. You’ll need to succeed on a MEDIUM Speech, Charisma, or Intimidation check to convince the guards to let her treat the prisoners. Barring that, you can get into a fistfight to push the issue.

Once that’s done, ask Klara how else you can help and she’ll send you to three injured soldiers down at the west side of the fortress. On your way there, pick up the following items:

Two bottles of Schnapps. One from the kitchen and the other from the Smithy’s room where Godwin is resting.

Bandages, Schnapps, Painkiller Brew, and Chamomile Brew in Klara’s cabin. The brews and Schnapps are in a chest in the loft.

Then, take those items down to the injured men. To treat them, you'll need to succeed at Survival, Alchemy, and Craftsman skill check to help you diagnose them. If you can pass enough checks, you'll get the prompts needed to treat them.

Mark
He has a cut on his head and leg. If you can diagnose him successfully, you’ll get the option to tell him “I’ll clean your wounds, just don’t fall asleep.” Then:

- Clean his wound with Schnapps.
- Dress the wound.
- Give him the Weak Painkiller Brew.
- DON’T give him a sip of liquor.

Kozliek
Kozliek is next to Mark, if you can diagnose him, then follow these steps:

- Give him a potion for his fever. A Fever Tonicum would be best if you have one but a Marigold Decoction or Painkiller Brew will do too.
- Clean his wound with Schnapps.
- Cauterize the wound. (Lead ball needed)
- Change his bandage.

Zwerk
Zwerk is underground. You can reach him by taking the stairs near Mark. If you can diagnose him, follow these steps:

- Clean his wound with Schnapps.
- Sew up his wounds. (Tailor kit needed)
- Rub the Weak Chamomile Brew on his ankle.
- Dress his wounds.

Return to Klara and tell her you’ve treated the wounded. When given the opportunity you can say “No walk today, I reckon?” and she’ll promise to meet you in bed later.