Need Hans's help in *Kingdom Come: Deliverance 2*'s "For Whom the Bell Tolls" quest? You'll need to brew a Fever Tonic to save the day. Here's how:
Fever Tonic Recipe and Location in *Kingdom Come: Deliverance 2*

The Fever Tonic recipe resides within the Surgeon's Workshop in Trosky Castle. Access is achieved in two ways: sneak in, or convince the Chamberlain. To persuade the Chamberlain, promise him a digestive potion. Successfully completing skill checks will grant you access. Alternatively, after delivering the horseshoe in "For Whom the Bell Tolls," speak with Cook Fanka. Offering to help with her locked chest leads you to the noble's kitchen and the ailing Chamberlain. Convincing him to let you help will also unlock the workshop.
If your persuasion fails, steal some food, exit the kitchen, and use the stairs leading to another kitchen. Bribe the guard with the stolen food, then sneak upstairs to the Surgeon's Workshop. There, you'll find the Physician's journal containing the recipe.

Brewing the Fever Tonic

The necessary herbs are already at the surgeon's station. Follow these steps:
- Pour wine into the cauldron.
- Add 3 handfuls of Feverfew.
- Lower the cauldron and boil for 2 turns of the sandglass.
- Grind a handful of Elderberry Leaves.
- Add the ground Elderberry Leaves.
- Add 2 handfuls of Ginger.
- Grab a phial from the bottom-left shelf.
- Distill the tonic using the Still.
Don't worry about failures; there are plenty of herbs available.
Once you've brewed the Fever Tonic, locate Thomas. If you gained the Chamberlain's trust, return with both the Fever Tonic and the Digestive Potion. Otherwise, use the noble's kitchen to sneak to the chapel and find Thomas and Adele. Speak with Adele to complete the quest.