If you are playing on one of the two highest difficulties then you should have automatically started with a Swallow potion. Assuming you haven't already used that potion you may give it to Lena. If you have already used the potion or don't have one, you will need to brew one which requires you to find the ingredients and then craft it in your inventory. The recipe calls for:
Getting the ingredients
The dwarven spirit can be purchased from the tavern keeper in White Orchard or crafted if you don't want to pay for it. A Dwarven spirit can also spawn in a lootable sack in the western-most corner of the alchemist's garden.
The drowner brain can be looted from the drops of drowners you kill. Search along the river coast for drowners, especially between White Orchard and the Nilfgaardian Garrison or near the Ransacked Village.
The celandine grows in many of the fields surrounding White Orchard, especially between the village center and the herbalist's house. Once you have the alchemy ingredients simply craft the potion in the alchemy section of your character menu. Additionally, the quest Precious Cargo will reward you with the necessary celandine if you choose to keep the contents of the locked chest.
Take the potion to the herbalist
With the potion in your inventory talk to Tomira and say "Got a potion for Lena." and the quest will be complete. Make sure to read the book as well, which will unlock several bestiary entries and a couple decoction formulas.
- Once again Geralt had a near impossible choice to make - a choice between a greater and lesser evil. While preparing to hunt the griffin, he had come across one of the beast's victims - a simple peasant woman named Lena. She had been on her way to meet her lover when the griffin attacked. The beast had mortally wounded her. A witcher's potion could save her life... or cause her to perish in agony.
- If Geralt helps her:
- The witcher decided to help Lena. Geralt then left White Orchard before he could learn the results of the risky treatment he applied. Soon afterwards, while visiting the Nilfgaardian garrison in Velen, he learned the woman had survived. The imperial infantryman with whom she was to meet the ill-fated evening of the griffin's attack had brought her to a nearby village. Sadly, none of this denoted a happy ending. Though the wounds on Lena's body healed, the toxins in the witcher's brew had melted her mind. This was not the first time a cure had proven worse than the disease.
- If Geralt doesn't help out:
- They say witchers do not feel as humans do. That they are stripped of emotion, untroubled by doubts and dilemmas. This might be true for some of the caste-Lambert possibly being a case in point. But there is no doubt Geralt was different. He honestly debated what to do with Lena, considered what would be the lesser evil, and did so for so long that the woman finally succumbed to her wounds.
- Brew a dose of the Swallow potion.
- Take the potion to the herbalist.
- Oddly, if Lena is helped, the quest automatically updates to reflect information that Geralt doesn't learn until he's in Velen.
- The quest will automatically fail if the player finishes up the prologue and leaves White Orchard before finishing this quest.
- If Geralt chooses to use the potion on Lena, a Nilfgaardian soldier of her acquaintance will later speak to Geralt about her condition as he approaches the Nilfgaardian Army Group 'Center' Camp in Velen.