Chicago--the reigning #1 city in homicides--has no shortage of deadly gangs. And all those gangs know well that the Cross crew occupies a cinderblock bunker called Red 71 . . . the last place you want to go, unless you're willing to risk it being the last place you go. The crew is notorious for its deadly efficiency and its disinterest in anything but money. So why has it turned from seller to buyer, grabbing up houses on a decaying block where only...