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Franklin can help Packie McReary during a heist, and he will become a crew member.
Johnny Klebitz from The Lost And Damned accuses Trevor of sleeping with his girlfriend, Ashley.
In the first mission for setting up the jewelry heist, when Lester is telling Michael that all the old crew is gone, he mentions a Eastern European guy from Liberty City.
Play the mission as Michael for the FIB to steal the supposed nerve agent that actually turns out to be perfume from what the radio says. The gentleman in the suit with glasses who works for the lab that you are stealing from tells the guards to detain the FIB agent, who shoots himself in the leg to cover for his friends, is the same person known as Edward T. Fortune that gives Nikko the information he seeks in return for him doing missions for the United Liberty Paper in Grand Theft Auto 4.
When in Michael's home, zoom into Jimmy when he is using his laptop at the dinner table. You can see a him viewing the LifeInvader profile for Niko Bellic.