In *Kingdom Come: Deliverance 2*'s "For Whom the Bell Tolls" quest, you'll need to brew a Fever Tonic to help advance the story. This guide details how to obtain the recipe and craft this crucial potion.
Fever Tonic Recipe Location and Acquisition

The Fever Tonic recipe resides within the Surgeon's Workshop in Trosky Castle. Accessing the workshop can be achieved through stealth or diplomacy. Sneaking in is an option, but a more engaging approach involves convincing the castle Chamberlain you can create a digestive potion for his stomach ailment. Successful persuasion grants you access to the workshop.
Alternatively, after delivering the horseshoe in "For Whom the Bell Tolls," speak with Cook Fanka at the forge. Offer assistance with her locked chest, leading you to the noble's kitchen. Here, you'll find the ailing Chamberlain. Successfully completing skill checks during conversation will earn his trust and unlock the Surgeon's Workshop. Crafting a digestive potion alongside the Fever Tonic further solidifies this trust, allowing you to meet Thomas.
Should your persuasion attempts fail, steal some food, exit the kitchen, and use the stairs leading to another kitchen. A guard is present; offer the stolen food to appease him. Once he leaves, you can sneak upstairs to the Surgeon's Workshop.

Inside, locate the Physician's journal on the bookshelf. This journal contains the Fever Tonic recipe.
Brewing the Fever Tonic

The necessary herbs are already prepared on 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 using the mortar and pestle.
- Add the ground Elderberry Leaves.
- Add 2 handfuls of Ginger.
- Take a phial from the bottom left shelf.
- Distill the tonic using the Still.
Don't worry about failures; ample herbs are available, including those within the room's chest.
Once you’ve brewed the Fever Tonic, deliver it to Thomas. If you gained the Chamberlain's trust with the digestive potion, return to him with both potions. Otherwise, use the noble's kitchen to reach Thomas and his sister, Adele, in the chapel. Speaking with Adele concludes the quest.