While exploring The Meadows, you will find two cows.
Talk to them to learn their story - these are a couple of people, who were altered. You will be asked to reverse the curse.
In order to do that, go to the witch - her house is right near the cows. You can use the key, which is lying nearby, or destroy the door. Unfortunately, there's a hatch there, which is also locked. You will need level 4 of thievery to open that entrance. If you don't have that, you will need to get to Cloisterwood and obtain the key from the Corpse Of Alice Alisceon.
This fight is very difficult. Alice uses fire totems and is healed by fire. Try to lure her out of the fire and get one of your team members to focus on destroying the totems. If you win, take the key from Alice.
Go back to the cottage and to the basement. The main room, leading to the office, is full of exploding rats. Each rat you kill will be replaced by a new one. To stop that, you will have to destroy their nests, located at the walls.
In the Alice's office, you will find the Witch's Potion, which will allow you to lift the curse from one cow.
Note: if you decide to drink the potion, you will be turned into a cow. You will get 10775 experience points and the quest will end.
You will also see a trapped frog there. There is a book there, containing all formulas of the witch. In order to read them, you will need a Scholar and Mystic. If nobody in your team has both these tags, here's the recipe: Augemator + Boletus + Witch's Eye. Augemator can be found in Cloisterwood; Boletus is sold in Driftwood; and Witch's Eye is in the witch's house.
Give the potion to the cows after brewing it.
Reward: 80700 experience points