How do you get Jaheiras harpers quest?

I've heard of it but I can't figure out how to start it...

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Eventually, you will rescue a man named Renfield from three or four goons in a random encounter. He has been magically poisoned, and he will ask you to take him to a man named Rylock in the Docks District. Accept this quest and you will eventually meet Xzar, who asks you to find his old buddy Montaron. When/if you accept, you have begun the Harper's quest.

Anyone can do that quest with or without Jahiera, I think he means the Jahiera romance harper battles. A romance with Jahiera has to be started before harpers start popping up.

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"In Ankh-Morpork curiosity killed the cat, tied weights to its legs and then threw it in the river."

Tiax, warmaster of clan HADB