Sonja Sohn stood in front of her audience, confident about the performance she was about to give. This wasn’t surprising, considering her history as an actress who was just coming off a five-year run as Det. Shakima “Kima” Greggs on HBO’s “The Wire,” one of the most critically acclaimed shows in television history. To project professionalism, she had pulled her hair back and was wearing pressed slacks and a collared shirt. Her motivation was clear, her research was done, and after many months of preparation, she was ready.

There was no script, though. Her “stage” was a classroom at the University of Maryland School of Social Work, and her “audience” — made up of teenagers and young adults whose lives could have beenmined for “The Wire” — wasn’t about to grant her anything based on her past credits. Not 18-year-old Tyrea Daniels, who guesses he had been arrested eight or nine times by then for selling drugs and stealing cars; 16-year-old Latavia Cornish, who says she was “always outside, stealing, getting locked up”; or 21-year-old Sean Hawkins, who had been “thuggin’ it up” since he dropped out of high school, “selling drugs, partying, stealing, robbing everything in sight.” They and about 15 people from similar backgrounds were slouched in their chairs, warily eyeing Sohn and each other.

This was late in 2009, during the first session of ReWired for Life, a program Sohn had conceived of years earlier and devoted herself to building after “The Wire” signed off. She hadn’t been ready to leave the show behind, neither what it stood for nor the Baltimore streets on which it had filmed. It was more than that, though. “I had an extraordinarily strong sense of purpose,” she says, in the same half-purr, half-growl voice familiar to fans of “The Wire.” “My entire life had become about this.”

All of which meant little to Daniels, Cornish and Hawkins. It was cool to meet Kima because they had loved the sho...