The squad is called in to investigate the death of Detective Sergeant John Van Impe, and are soon faced with two suspects -- the officer's younger partner, Wayne Tocchet, and a long-time informant who fled the scene, Marlon Cummins. As the investigation continues, the squad begins to realise that they may have to arrest one of their own.

A failed bank heist brings low police morale to the surface.

The Russian Mafia is suspected of a celebrity's shooting.

Pogue and Oosterhuis investigate when a young girl named Erica Warner is taken from in front of a local store, with her older sister Shannon as the only witness. While Oosterhuis questions Shannon, he can't help but see similarities between the two of them, because when he was 13 he once lost track of his little brother at a carnival for a few hours and felt responsible for years. The squad soon realises that Erica's disappearance as a lot in common with that of a young girl who disappeared three years earlier, and they're determined to find Erica and stop the kidnapper before he can take another young girl from her home.

The squad gets involved when a shoot-out in a market leaves a popular officer paralyzed from the waist down. It doesn't take long before they realise that a bounty hunter is after the men in question, all of whom seem to be on the run from various conviction threats in the U.S.

A psychiatrist is found murdered at a criminally insane hospital.

The officers discover that mysterious deaths at a hospital may be somehow linked with unsolved deaths.

When Blair Patterson's beheaded body is found in a van that's been sitting in a neighborhood for days, his wife turns the squad onto Emily Glover, a tenant in the apartment building Blair managed, who immediately confesses to his murder and claims she and Blair were killing couples throughout the city. When another couple is found dead in the same way as the others, the squad realises that something with Emily's story is off, and it's up to Oosterhuis to try to get it out of her as Emily will not talk to a female detective, and has already given up on Weeks.

When a politician and his wife are found dead, the squad initially suspects that it may be a murder/suicide.

An alliance between a detective and a criminal create deadly consequences.

The officers must investigate an assault on two women.

When Amber Watley calls to report the body of a young man by the tracks, the squad immediately moves in to investigate, but it doesn't take long before Weeks and Gillam realise that there is no way it happened the way that she said it did. As the squad continues to investigate the death of Donnie Tenio, they soon discover that the problems in the group of teens go far deeper than they could have imagined.