One Last Thing
This mission is the final one given to you by Jimmy Pegorino. It's not technically a mission, just a cutscene. In the cutscene Niko meets up with Pegorino after killing or sparing Darko.
Head over to Jimmy's club in Tudor. Niko is seen relaxing at a seat when an angered Pegorino runs over to him and explains that he needs your help with a deal including Dimitri, the snake that betrayed you back in Hove Beach. Niko says multiple times to Jimmy, he has had "history" with Rascalov.