Main characters
Mary Shannon (Mary McCormack): Mary is a capable officer, a nonconformist uninterested in typical feminine wiles. To her witnesses, she is known as Mary Shepard. She has trust and abandonment issues that lead her to have difficulties with relationships due to a difficult childhood resulting from her fugitive father's abandonment and her mother's alcoholism. During the first two seasons, Mary dates Raphael "Raph" Ramirez, a minor-league baseball player, and they eventually become engaged; however, she often seems unhappy with the relationship and the engagement, and her feelings of doubt about marriage cause Raphael to call off the engagement during the third season. During the fourth season, she has a one-night stand with her ex-husband, Mark, and becomes pregnant. Throughout her pregnancy, Mary is convinced that she wants to give the baby up for adoption and becomes agitated whenever everyone around her starts treating her differently. In the season-four finale, "Something Borrowed, Something Blew Up", she goes into premature labor. In the season-five premiere, "The Anti-Social Network", after Mary gave birth to a daughter, she changed her mind about giving her up and decided to keep her because she felt that no one could protect her baby better than she could. She names her daughter Norah Shannon, and shares custody with Mark. During the final season, she meets and begins a relationship with Kenny, a single dad.
Marshall Mann (Fred Weller): A fifth-generation deputy U.S. marshal, to his witnesses, he is known as Marshall Miller. Marshall Mann is Mary's partner, as well as her best (and only) friend, and occasionally appeared to desire more than her friendship as the series progressed. Laconic and laid-back, he seems to know a little about everything, what Mary calls "useless information", and is rarely ever speechless. The only time this has ever happened was in the season-three episode "Whistle Stop", when he discovered Raphael and Mary had broken up, leading her to declare him "verbally impotent". Friction between Marshall and Mary occurs at times, often due to Marshall's cerebral approach and Mary's gut instinct, though both are extremely protective of witnesses and each other. Though Mary and Marshall have occasionally disagreed about the proper course of action regarding policies, Marshall has typically backed down after taking time to get a perspective and will adopt Mary's position if her cause is right—even when her attitude is not. In later seasons, Marshall begins a relationship with Detective Abigail Chaffee of the Albuquerque police force. Abigail and he eventually move in together and ultimately become engaged. In the series finale, he is made chief inspector for WITSEC's southwest region.
Stan McQueen (Paul Ben-Victor): As chief inspector for WITSEC's southwest region, Stan is Marshall and Mary's boss. He is a flexible boss and stand-up guy, quickly backing up both Marshall and Mary when they hit trouble. Stan likes to stick to official WITSEC doctrine as often as possible and is reluctant to bend the rules without authorization. Stan has made an effort to recreate the professional distance in his office, presumably as a way to shield his team from FBI fallout. During the second season, Eleanor and he have a one-time intimate encounter. In the final season, he begins a relationship with his dance instructor, Lia Hernandez, and gets promoted to chief deputy director of WITSEC in Washington, DC.
Jinx Shannon (Lesley Ann Warren): Mary's alcoholic mother, she was abandoned by her bank-robbing husband to raise her two daughters alone. Although she adores her daughters, she has never been a traditional, supportive, job-holding, maternal figure. She recognizes that Mary is the stable member of their family, and this has inspired her to live up to her daughter's example. Even so, she initially harbors a great deal of resentment against her strong-willed daughter, though this only comes to the surface when she is under great emotional duress. Firmly on the path to recovery, Jinx slowly grows into her own woman, apart from the conniving lifestyle she once enjoyed while being an alcoholic. Currently sober, she still follows Mary's lead, but is slowly becoming more reliable now, having a job and a house of her own. In the final season, she goes to Miami to support Brandi while she is going through rehabilitation for alcoholism.
Brandi Shannon (Nichole Hiltz): Mary's younger sister, she is very much her mother's daughter and the baby of the family. She lives in the moment and was originally involved with a shady man named Chuck. Despite this, she looks up to Mary, and at times, sees her as an example. She also tends to be the more mature figure in her relationship with her mother. Brandi is loyal to a fault, but is slowly developing a conscience independent of others' approval. Moved by seeing a young infant in the hands of a meth addict and a drug-dealing boyfriend, Brandi backed out of a drug deal initiated by Chuck so child services would protect the baby. Later, once Mary was rescued from her abduction (which was a fallout from this decision), Brandi later admits privately that if she had known how the events would play out, she would have killed Chuck herself rather than let her sister come into harm's way from her actions. During the second season, she meets and dates Peter Alpert, a man she met in Alcoholics Anonymous, who later turned out to be very rich (Mary stated he "owns half of Albuquerque"). Brandi takes this information differently, believing she is just "one of his girls" and initially tries to act selfishly to have him break up with her. After he stays with her (even offering hang-over remedies), he states his desire that they continue to date, to which she agrees. Brandi eventually moves in with Peter, and in the beginning of the fourth season, she informs Mary that Peter and she are engaged. However, in the season-four finale "Something Borrowed, Something Blew Up", Brandi feels ill-equipped to marry Peter and live as his high-class wife, and she suffers a breakdown on her wedding day and leaves Peter at the altar. During season five, since the wedding fiasco, she has developed a drinking problem, and with the support of Jinx, enters a rehabilitation program. In the series finale, she returns and is revealed to be pregnant, and tells Mary she has decided to keep the baby and move back home to Albuquerque to be near their family.
Detective Abigail Chaffee (Rachel Boston): Albuquerque Police Department detective and Marshall's girlfriend, Abigail is extremely outgoing and friendly, much to the annoyance of Mary. During the final season, Marshall proposes to Abigail and she accepts. Later, Abigail tells Marshall he needs to make their relationship a bigger priority than Mary if their relationship is too stand a chance.
Delia Parmalee (Tangie Ambrose): A new WITSEC inspector, she joins the cast in season four. She is known for her cheerful, optimistic attitude despite the seriousness of her job.
