Lindsay, Claire and Jill cautiously welcome a new member to the Women's Murder Club, young reporter Cindy. Meanwhile, Lindsay and Jacobi investigate a homicide committed by a serial murderer dubbed "The Vendetta Killer". In their private lives, Lindsay faces up to the past when her ex-husband is brought into her police department in a leadership role, Jill faces a domestic crisis, and Claire struggles to help her husband, who's fighting depression.

Lindsay and Jacobi hunt down a killer who committed a triple homicide on a subway car, and discover a disturbing twist in the killer's motive. Cindy tries to gain the respect of The Club. Jill prepares to move in with Luke. Claire helps Ed through his recovery. Lindsay meets Tom's fiancée.

While investigating a woman found dead in a parking lot, Jill bonds with the victim's teenage daughter. Meanwhile, Lindsay returns to the dating scene and Claire attempts to bring the romance back into her marriage.

The Club investigates an underground drug ring that's being run out of a nursing home. Lindsay goes on a date. Jill makes a huge decision in her relationship with Luke.

Lindsay and Jill contemplate their own biological clocks when The Club investigate the murder of a young man and the disappearance of his pregnant wife.

An NFL quarterback is found dead in his hot tub, with his family believing it was suicide. But the Club think differently. Meanwhile, Lindsay crosses paths with an NFL star who was friends with the dead man.

The Club investigate the murder of an illegal immigrant, where the only witnesses are the victim's father (who was also shot), and his young daughter. Meanwhile, Lindsay calls in Heather to get through to the girl, and Jill turns to Denise for help when an immigration official turns up.

The Club delve into San Francisco's drag queen community while investigating a murder. Meanwhile, Tom and Heather tie the knot, and Luke finally discovers the truth about Jill and Hanson's affair.

The Club investigate the decapitation of a wine broker, and suspicion falls on his business partner. Agent Ashe tries to get Lindsay to investigate the Kiss Me Not Killer with him, and Lindsay is forced to come clean over the threat on her life. Tom and Heather return from their honeymoon.

Lindsay bends the rules while investigating the murder of an undercover cop, and gets a rude awakening when her dirty ex-cop father suddenly reappears in her life. Meanwhile, Cindy still feels distant from the rest of The Club and Lindsay meets a handsome stranger.

Both Lindsay and Jill question their ethics over a rape suspect who is found murdered. Meanwhile, Lindsay considers taking her relationship with Pete to a new level.

Lindsay risks the lives of both herself and her father in an effort to capture the Kiss Me Not Killer once and for all, when a woman's kidnapping leads to the killer's identity being revealed to The Club.