like Primo says above. Also, a prisoner may try to exploit any bit of info he can find.

Predator finds out someone's (the prey) uncle is more like a father to him than an uncle and owns a small grocery. Predator gets a couple guys to threaten prey either with physical or sexual violence. Predator comes along and saves the day. Then the favors start.

A million ways that scenario can play out. The above is the nice way, sadly.

Or, predator gets someone on the outside to threaten the uncle, maybe rough him up a bit. Now the prey can be used to exploit his job or whatever. If he doesn't smuggle food (for instance) the uncle really gets fucked up. Could be for food, sex, a phone card, anything.

A story from a mafia book I can't remember the title of: mafioso gets sent to prison where a guard is personally fucking with him. Mafioso gets someone to snap a photo of guard's little girl in the schoolyard playing and send it to him. Mafioso walks up to guard and hands it to him saying "See, it's that easy." No more problems.