Early one morning in a New York City park, a passerby walking his dog discovers who ends up being a Jane Doe shot dead in the front passenger seat of a parked car. Homicide Chief Captain Lundquist assigns longtime Homicide Detective, hard-boiled and grizzled Lieutenant Corrigan in charge of the investigation. He also assigns as co-lead younger college educated Detective Frank Tobin, newly transferred into Homicide from the Police Laboratory. While Tobin, who is used to having his head above a microscope in conducting his work, realizes that he has to gain the skills of field work on the job, rough around the edges Corrigan is not looking forward to working with who he considers an egghead. They have to discover not only the victim's identity, but who killed her, why she was killed and the killer's whereabouts, Tobin determining early in the investigation that the killer is indeed a man and a tall one at that. One of the other major leads is the tattoo on the victim's wrist. In the process of their investigation, Corrigan and Tobin will either complement each other in their different working styles, or drive each other crazy in those differences. In following another lead, Tobin meets botanist Dr. Mary Maher, association with who he may want to extend beyond this case in his attraction to her.