This drama revolves around a U.S. Marshal, Mary Shannon (Mary McCormack), who works with the Federal Witness Protection Program (WITSEC). She doesn’t respond well to authority and refuses to conform but has a soft spot for the witnesses (who know her as Mary Shepard). She has trust and abandonment issues that in part stem back to her father’s gambling and mother’s alcoholism.

Mary’s partner Marshall Mann (Fred Weller) is the fifth generation of marshals in his family. He sometimes seems to want more from Mary than just friendship. He’s of help on many cases, since he seems to know a little about everything. Although he and Mary take different approaches and don’t always agree, Marshall will usually back down to her. He’s known as Marshal Miller to the witnesses. Their boss is Stan McQueen (Paul Ben-Victor), a man who always backs them up but doesn’t like to bend the rules. He once spent the night with Eleanor (Holly Maples), the recently widowed office manager.

Jinx (Lesley Ann Warren), Mary’s mother, is not your typical mom. She would do anything for her daughters, but is anything but maternal. She sees Mary for the stable person she is and wants to live up to her example as she starts over, trying to recover from her alcoholism and attending AA meetings as ordered by the courts. Brandi (Nichole Hiltz) is Jinx’ younger daughter and the one that makes foolish choices, like her mom. She was involved with a drug dealer who ended up getting the whole family in trouble. She attended Jinx’ AA meetings for her, pretending to be Jinx, and met Peter (Joshua Malina). She eventually admitted the truth to him and they started dating.

Mary has an on-again off-again relationship with Raphael Ramirez (Cristian de la Fuente), a minor league baseball player. He made it to the majors but was injured. Brandi helped him rehabilitiate and was attracted to him, but he remained faithful to Mary. He retired from baseball and began working as a car salesman for Peter Alpert (Joshua Malina), Brandi’s boyfriend.