When a young mother is found naked and strangled in her car, Tulsa Detective John Brown uncovers a dark obsession that may have turned deadly.

In Tulsa, an innocent mother is viciously murdered with a butcher knife. While in Atlanta, a beloved patriarch is gunned down when a game of dominoes turns deadly.

In the season premiere, an Atlanta woman is strangled and the investigation unearths more potential crimes.

In New Orleans, a transgender female is shot four times - the victim of an apparent robbery. In Atlanta, two men draw guns in an underground mall, but only one survives.

A double killing on New Orleans' Bourbon Street leaves the city on edge; Tulsa, Oklahoma, detectives believe that a shooting victim may have been lured into a trap.

A violent attack in a Tulsa, Okla., barbershop leaves an employee dead and numerous people wounded; the hunt begins for a killer with an AK-47 assault rifle.

A New Orleans father and his friends are ambushed while sitting in a parked car; a feud between households in an Atlanta apartment complex leads to the killing of a promising boxer.

When an Atlanta father of two is gunned down with an AK-47, rookie detective Scott Berhalter must sift through lies and alibis to get his killers off the street.

In New Orleans, a man is executed in broad daylight, and Detective Ryan Vaught must battle fear and distrust on the street to identify the killer. And in Minneapolis, when a teenager is murdered at home, Sargent Christopher Gaiters' best hope for finding the killer is the victim's father, who witnessed the shooting.

When a popular New Orleans hip-hop promoter is gunned down next to his limousine, the search for the killer leads Detective Clinton Givens to more than he bargained for. In Tulsa, a friendly night of drinking at a senior center apartment complex leaves one man dead and another wounded. Detective Mark Kennedy must find a third man who was there to uncover what happened.

The case of a young New Orleans mother who was ambushed at home and fatally shot hinges on the eyewitness account of a 4-year-old girl.

A Tulsa, Okla., detective hunts a family of elusive criminals after a former Marine is fatally shot while trying to recover his stolen bicycle.

A Tulsa, Okla., detective pieces together fragmented accounts from five potential witnesses as he investigates a crime involving a lethal combination of guns and meth.

In Tulsa, a young mother of four is found shot on the side of the road. Detectives' only clue is a photograph she took just moments before her murder.

Detective Rob Barrere investigates when three men meet in a motel room in New Orleans east, and one of them ends up dead; while in Tulsa, Detective Ronnie Leatherman catches the case of a man stabbed 21 times when a night of drinking ignites a murderous rage.

A killer terrorizes Atlanta and investigators try to track him down.

When a young woman is executed on a street corner in Tulsa, investigator Nathan Schilling discovers her friends may be hiding information about the murder.

Police must wade through a web of secrets and lies when a man is found dead in his Tulsa, Okla., hotel room.

A young father is killed while visiting his son in Tulsa and a home invasion kills one teenager and leaves two more wounded in Atlanta.

A young New Orleans mother is found shot and burned in the trunk of her car following a night out on the town.

In Atlanta, a caretaker is gunned down over a grudge. And in Tulsa, a young man loses his life when a bully goes too far.

When a young man is shot to death at a motel party, Tulsa Detective Justin Ritter discovers a photo posted on Facebook may have triggered a dangerous chain of events.

In Atlanta, a young father is gunned down by a brutal robbing crew and Detective Tracy Lewis discovers on her first case that she may be chasing the wrong suspect.

An Atlanta man is gunned down in his home by an AK-47; the victim's wife holds a dark secret that could tear the family apart.

Investigating a mass shooting in New Orleans.