Kat Farmer was an expert pickpocket and an old friend of Sean and Emma Kennedy.

Although she and Sean had not seen each other for three years, Sean still remembered her affectionately, Kat expressing admiration for the way that the Kennedys had always looked out for each other where her own sister hated her. Since she had last seen the Kennedys, Kat had also become a mother to a two-year-old daughter, Laurel- her relationship with her mother also improving-, although she had not seen Laurel's father for over two years.

Kat came back into contact with Sean when she was arrested by corrupt DI Sidney Fisk, who was attempting to imprison the team for a criminal contact of his. In order to escape prison after Fisk claimed that drugs were found on her, Kat was forced to infiltrate the gang and help to sabotage their con against Linda Runcorn, an online travel critic, setting up a meeting with Sean at a bar and asking for a job to earn some additional money.

Although Kat's pickpocketing skills proved vital in helping the gang sell the con to Runcorn, she was forced to plant drugs on Emma on Fisk's orders. Although the gang forced to leave Emma in prison while trying to complete the con, it was subsequently revealed that the entire con was actually set to target Fisk- even Runcorn was just an alias for another grifter-, the team using Kat to give Fisk fake information about the con.

With the con concluded, Sean contacted Kat and assured her that he didn't blame her for her actions, recognising that her daughter had to be her priority, even giving her a share of the money they had made during the con as agreed.