When a city-wide outbreak of a mysterious and lethal virus occurs, even Megan and her team are at risk. In order to determine who and what caused this outbreak, CDC Officer Charlie Stafford takes over the investigation.

The team needs to quickly figure out how to treat the virus when more and more people are becoming ill and dying.

Megan comes face-to-face with a convicted serial killer she helped put away.

The parents of a seemingly perfect family are murdered; Curtis grapples with his new position; Megan's romantic life heats up.

When a young nanny is run down by a car and killed, the 5-year-old child she was watching is kidnapped; an interrogation goes awry.

When a recent lottery winner is found brutally murdered, everyone becomes a suspect.

When two young girls are in a tragic car accident, one is left in critical condition and the other is found dead at the scene. As Megan and her team investigate the case, however, they realize there has been an awful mistake. Not only was the wrong girl pronounced dead, but the car accident may not have been the actual cause of death.

Many suspects emerge after a rich tycoon's new, young wife is shot during a deer hunt; Kate and Megan's relationship takes a turn for the worse.

A murdered young woman's body turns up in place of a medical school cadaver during class, leaving Megan to rely on the aid of the star student to help solve the case.

When a woman suspected of murdering her son is found innocent, Megan and the team try to identify the real killer; an overzealous reporter makes the investigation difficult by sensationalizing the case.

When the owner of a family owned and operated Italian restaurant turns up dead in the freezer, Dr. Hunt and the team take a closer look into family matters. Meanwhile, Peter must face his own haunted past.

After a car accident reveals a dead body in the trunk, the team is led to another body, giving the team two cases to solve; Megan is reconnected with an old acquaintance; Kate's job is threatened.

The investigation into a fatal car crash reveals the seedy underbelly of a perfect-looking neighborhood.

After Peter rescues a woman from a house fire, Megan discovers another person in the house who died. Peter takes the discovery personally since he had no idea anyone else was in the house. A veteran arson investigator challenges Megan at each step in her investigation. When Megan complains to Kate the response she gets only intensifies the tension between the two women.

A champion equestrian is killed and potential drug use is suspected, but when Megan's daughter, who also rides, overhears details of the case, she leads the team to a clue and possibly the murderer.

A pharmaceutical rep is found dead in the Schuykill River, but when Megan Hunt and the team investigate, there's no blood found in her body. The team must locate the original crime scene to see if they can find the cause of death, but with suspects who have access to hundreds of unknown drugs, they may never know who or what killed her.

An undercover cop is discovered murdered at a truck stop.

A new investigation is opened up after a man assumed to be dead disappears off Ethan's exam table. When another body is found, it's the DNA evidence that leads to an eye-opening discovery.

Megan investigates the death of a bride on her wedding day; Ethan has a crush on the new girl, but she is interested in someone else.

When a popular 17-year-old high school student is found dead after a rave, the team must decipher various unknown drugs in his system and multiple bruises to figure out the cause of death. Meanwhile, Meghan is finally starting to date again after the divorce, but her ex-husband springs some shocking news on her and her daughter, causing tension at home.