Hardass Detective Caitlyn "Cat" Sullivan, a woman hell-bent on finding her father's killer, is demoted to foot patrol for reckless driving, disobeying orders, and personality conflicts. Cat arrests Marseille born taxi driver Leo Romba, a highly skilled driver with a past. Accused of being a wheelman in a bank robbery, Leo begs Cat to make a deal: in exchange for proving his innocence, he will provide her with his driving skills and taxi. The unlikely partnership grows into friendship as they investigate a series of robberies, and Leo becomes Cat's confidant in her ...
Cat becomes responsible for Leo. Cat and Leo try to figure out the cause of death of a holocaust survivor who is a close friend to Leo. Cat also reunites with her best friend which leads as an insight into her father's murder.
Cat and Leo figure out the unusual death of a foster woman when kids are involved. Cat and Leo chase after a kid after he runs away. Cat secretly furthers an investigation on her long lost best friend Annabel Capella.
During a prison transfer, the truck is ambushed. Most of the prisoners escape and a few of them die including the driver. Cat soon realizes that the only witness to her father's murder was one of the few girls who had escaped the ambush. Cat and Leo then finds a way to find her and the other inmates. Cat sets her mum up on a date with her boss. Cat allows her ex-husband Gregg take credit for the ambush arrest if he helps her find Ellie Wilson and the undercover agent who had previously helped her.
Cat's buried emotions are brought to the forefront when Amanda Pearson , the wife of the Park Slope Stalker, is found murdered. The stalker case made Cat famous, and almost got her killed. When Baker asks her to take the lead, she hesitantly agrees, as long as Leo stays by her side. What they uncover is another stalker out to kill Cat.
Three men are found dead under mysterious circumstances, but similarities in their physique and taste in watches seems to point to one murderer, a Black Widow. "She mates and then she kills." Leo fits the profile of the victims and agrees to go undercover as bait to catch the killer, putting his life in danger.
Walking the streets of Brooklyn, Cat and Leo discover a dead man in a dumpster, or at least they thought he was dead. The man was exposed to some sort of weaponized toxin and his rambling words are Apocalyptic. The NYPD goes into high terror alert as they rush to control the possibility of mass exposure. Leo's convinced it's a Zombie outbreak, but Caitlyn uncovers a terrorist plot.
A blackout puts half of Brooklyn in the dark. Cat arrests Styx, a member of the "Jungle K's" gang. Trying to escape, Styx kills two cops in the precinct. Everyone becomes a suspect when Cat discovers it was a planned hit and someone in the precinct gave Styx a gun. It's an intense and explosive showdown when Styx's gang shows up demanding his release and gunfire rains down on the precinct.