Pearl Callahan pulls her sedan to the side of Stockton Boulevard, just up from an abandoned house with boarded-up windows, somewhere near Sacramento’s southern city limits. Planted on the stoop is a young woman with stringy blonde hair, wearing sunglasses to cloak an already-dark night. Callahan, small and dainty under a canopy of bangs hedging her forehead, turns to her best friend, Kristen DiAngelo. They exchange a look. These onetime sex workers know a member of the tribe when they see her.