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Quest - Down The Drain
Quest Pickup - Hideout (I8) (Dimitri)
Quest Location - Hideout (C15)
Quest Finish Point - Hideout (I8) (Dimitri)
I actually could be wrong on the location of this quest as by the time I got this quest I was already quite far through the game, simple mission, take the zone, return to Dimitri, He will then offer to join you.