A messenger will tell Jan that his old love's child has become sick. And she asks for his help at his house. His house is in the southeastern part of the slums. There you will encounter the sick child and Jan's love. The child has some kind of "sickness of the mind" that can't be cured by conventional ways. After some dialogue someone suggests that you talk to the old crazy uncle in the basement. He suggests that you talk to the "hidden", when asked how he refers to a noble lady in the Government District. She will arrange a meeting with the "hidden" in the sewers of the Copper Cornet.

The hidden is waiting in the large sewer pipe with water flowing down the middle that runs northeast/southwest through the middle of the sewer map. The hidden is on the southwest side of the pipe, opposite the kobolds you fight as part of the talking sword quest. The hidden will require a task of you in order to help the sick child. You will have to kill some Giths in a room on the upper floor of the Five Flagons Inn in the Bridge District. Once you return to the sewers and talk to the hidden, the child will be cured. Return to Jan's home for some dialogue with the arse of a man that his love married. You get a decent amulet from the Giths that protect you from all psi attacks.

Also, at the end of the quest, Jan's lover goes back to her husband, and many people falsely think they have stuffed the quest, when it is just a sad ending. It is worth clarifying. Also, some people have said that Jan will NOT join back with them sometimes after the quest is done. It never happened to me, maybe it is a time or charisma thing.