A building collapses on one of Mary's witnesses, leaving him exposed to outside threats, so Mary has to risk her life in order to keep her witness safe.

An Orthodox Jew enters Witness Protection, but his wife refuses to join him. The situation is made more complicated by the fact he is being pursued by a man motivated by a higher authority.

An engineer blamed for a bridge collapse enters the program after being targeted by angry family members of the victims who died in the tragedy.

A dead witness causes Mary to take leave of her administrative duties to solve a "Ten Little Indians" story, until her plan gets changed by her own brand of Post-Traumatic Stress disorder.

FBI agent O'Connor arrests Brandi on charges of drug trafficking and murder. Insisting her sister is innocent, Mary works to help Brandi while ultimately trying to discover O'Connor's real motive for his actions.

Mary lends her expertise for the U.S. Marshalls by making a training video with a film crew. Elsewhere, Marshall prepares the arrangements so that an elderly mobster in Witsec can go to his son's funeral.

The US government helps a Latina political activist hide in Witsec, but the arrangement sours after she moves into her new home.

A northern California marijuana mastermind cannot testify without using the drug to neutralize his anxiety disorder.

When a series of murders seem to follow a new ex-con witness, including stabbing Mary's friend, she and Marshall have to figure out if he's the killer in time to save his next victim.

A world-class counterfeiter witness is suspected in a murder; Mary and Marshall realize they may be hiding a witness from the government.

A witness finds herself having difficulty in managing her own brood of children, so Mary offers to babysit the trio of problem kids.

Mary and Marshall find themselves in a difficult position when Stan's very first witness turns up dead and he is implicated in her murder.

The barely legal daughter of Mary's witness – a Miami racketeer – finds herself in a dangerous romance, just as Raph's mother visits to prepare an engagement feast for the surprised Mary.

When a Wall Street blue blood rats on his boss' investment fraud and hides out in WITSEC, something from his past life comes calling.

Mary briefs a new witness whose visitation rights with his son depend on the man's testimony. When Mary learns the boy is missing, she tries to find him.