This quest can be acquired from Sir Hans Capon a few days after completing the main quest 'The Hunt'. Go to his chambers in Pirkstein Castle to find him lying in his bed and speak with him to initiate the quest. Sir Hans suggests that you meet him in the evening at the bathhouse. Go to the baths and use the time dial to wait until evening. You will know that Sir Hans is present by the presence of his horse at the gate.
If you attempt to use the door too early, Sir Hans will ask you to wait until after dark. Use the time dial to wait until 22:00 and then enter the room. Speak with Sir Hans and exhaust the dialogue options. Play the game of dice with Zdena and then speak with Sir Hans to enter the bath.
After some time Henry will get out of the bath. Speak with Sir Hans about what is bothering him and he will send you on a quest to fetch some proper wine and a pitcher. Before you leave the room be sure to take the key labelled as 'Sir Hans Capon's Keys', which can be found in the chest next to the bath tub.
The pitcher and wine can be found in the cellar of the Rathaus. The door to the cellar can be found in the alley between the armourer and the weaponsmith.
At some point you will encounter a guard who patrols the storeroom and the cellar. You will have to inform him that you are fetching wine for Sir Hans. He will not believe you initially, so you will have to use your strongest persuasion skill to convince him.
You can now take the wine to Sir Hans. Upon your arrival at the bathhouse you will notice that the husband of one of the bath maids is attempting to drown Sir Hans. You will have to beat him in a fist fight. Once you have done that a cut scene will initiate in which Henry and Sir Hans continue drinking. You will then wake up the next morning with a hangover. Go to Pirkstein Castle to see how Sir Hans is doing and complete the quest.