A petty crook, Ricky (Tim deZarn), hoping to get a reduced sentence, relates witnessing a young man washing blood out of his car the night a teen track runner was murdered. The young athlete, Paige Pratt (Summer Glau), was found shot, and her boyfriend Al Clarkson (Doug Kruse) was originally imprisoned for the crime.

A college professor (Jeffrey Nordling), who lost everything − his career, his family, his reputation − after being suspected of murdering one of his female students (Kaitlin Doubleday) in 1995, offers new information regarding the case that he hopes will clear his name. He believes the student's death is connected to a copycat murder of a prostitute. Rush investigates the woman who was killed and the men in her life in order to discover which one of them killed her.

Det. Stillman asks Lilly to re-open a case he couldn't solve, wherein an 8-year-old boy, Tim Barnes, was murdered in 1980. The prime suspects included a catholic priest, three glue-sniffing teenagers, one elusive suspect, and the boy's own parents.

Rush and Valens re-open the case of a 25-year-old black woman, who was murdered in 1939, after the woman's granddaughter comes forward with new information. The woman was assumed to be a prostitute murdered by a client, but letters written by the victim indicate that she was afraid of a milkman.

Construction workers discover a skull with bullet hole under the ruins of a disco club burned down in 1978. 22 people died in the fire. Rush and Valens come to the conclusion that the burning of the club was arson, meant to cover up a murder leaving them with not one, but 23 cold cases.

The shooting death of a man in his driveway is connected to the unsolved 1992 murder of a Democratic campaign worker whose lifeless body was thrown into a nearby river on election night. The investigation centers on the relationship the dead woman had with a present-day congressman. Apparently, the victim in the current homicide probed into the earlier slaying and discovered damning new evidence. Elsewhere, Lilly spies Kite flirting with a new ADA and gets jealous.

When DNA evidence reveals that a wrong man was convicted for killing 15-year-old Eve Kendall back in 1986, the team re-opens her case in an attempt to find the real killer.

Lilly returns to her last case before joining the Cold Case Squad as she re-investigates the brutal triple homicide of a restaurant owner and his family, murdered in the restaurant bathroom in 2003. Also the other team member have personal reasons to closing the case; Jeffries grew up in the predominantly black neighborhood while Vera was the one assigned to the case when Det. Rush left.