Caitlin "Cat" Sullivan is an NYPD detective working in Brooklyn. After her driving privileges are suspended, she relies on Leo Romba, a highly skilled Brooklyn cab driver from France. Leo becomes Cats driver and a consultant on her cases. While solving crimes with Leo, Cat is also running her own unauthorized investigation into the death of her father, an NYPD detective thought to have been executed by the Capella crime family. In doing so, she clashes with her boss, Captain Baker, and her ex-husband Gregg, who has picked up the case for the FBI.