Lilly investigates an unsolved hit-and-run accident from New Year's Eve 1999 that left a man dead, after a recovering alcoholic comes forward and claims she is the one who hit him. But the evidence points to the guy being murdered, not accidentally run down.

When human remains are found outside a former state prison, the team re-opens the 1968 case of a dead inmate, murdered on the night Johnny Cash's Folsom Prison Concert was broadcast to prisons throughout the country. However, when it's revealed that the bones don't belong to the person everyone had assumed, the team must start the probe anew by first identifying who the victim was.

Rush and the team investigate the 1969 murder of a 19-year-old girl whose body was found in her boyfriend's apartment the day he fled to Canada to avoid fighting in Vietnam.

A convicted serial killer will be paroled after 25 years in prison unless Lilly and her team can connect him to the 1977 murder of a young doorman found strangled on a train platform. The killing is eerily similar to other murders committed by the man. Making the case more urgent is the fact that the convicted strangler hints that he will kill again upon release. Elsewhere, Scotty confronts Christina about her past and tries to get her to talk to a New York detective.

In 1954, 9-year-old Otis Petrowski last saw his mother in a mental institution. Now over 50 years later, after the death of an elderly woman who had been using Otis' mother's identity, Det. Rush sets out to discover what happened to the boy's real mother.

The 1998 case of a female drug smuggler is re-opened. The woman was involved with Scotty at the time he was working undercover on a high-profile drug case, and he has been keeping it a secret from the team for all these years.

The 1994 case of a raped and murdered 16-year-old girl is re-opened when Det. Jeffries gets a call from a prisoner on death-row -- scheduled to be executed in just three days.

The team re-opens the 2004 case of a female veteran of the Iraqi War when her prosthetic arm is found in a river. Meanwhile, Scotty visits his older brother in connection with a case that brings up painful memories from their childhood.

In 2002, two kids were shot in front of two different schools on the same day at precisely 8:03 a.m. It's the fifth anniversary of the shootings, and Kat Miller wants to re-open the murders because she feels the cases are connected.

In the fourth season finale, a hostage situation arises when the entire team is held captive while they're investigating the 2006 killings of a family who had just moved into a new house.

Recovered from the shooting, Lilly wants to convince her boss that she's ready to get back to work. The team re-opens the 1994 case of three 10-year-old kids who were beaten to death when Lilly suspects the teens convicted of the killings may have been wrongfully incarcerated.

When a severed hand is discovered at the scene of a drug bust, the team re-opens the 1997 case of a convicted criminal who was thought to be on the run from authorities all these years.

The team re-opens the 1951 case of a marine who went missing and never reported for duty after his shore leave.

When the mother of a missing team storms into station. The case of a witness protection member is reopened when his body is identified by the missing teen.

The team has to cope with their own emotions as they search for the shooter responsible for Jeffries' shooting.

With the team investigating the 1966 shipboard murder of a young woman traveling in steerage on a luxury ocean liner who was believed to have committed suicide by jumping overboard. But new evidence indicates otherwise. Meanwhile, the trial of a military academy official who attempted to harm Lilly begins.

Rush tries to ignore her father's appeals to give her troublemaker sister another chance after she suddenly resurfaces.