Two ex-boxer detectives - Dwight Bleichert (Josh Hartnett), a die-hard intent on serving and protecting and Lee Blanchard (Aaron Eckhart) - bond over their shared pasts, and Lee's girlfriend, Kay Lake (a beautifully lit Scarlett Johansson).

The boys are in the midst of chasing a bad guy when suddenly the body of the dismembered Smart is found a block away, her body cut in half and with all of her organs missing. Dwight and Lee are pulled off their case and assigned to the Dahlia task force. Dwight resents the assignment, but Lee becomes obsessed, popping pills to work around the clock.

While chasing down Short’s acquaintances, Bucky finds time to bed the luscious Madeleine, a socialite who might be the killer (Hilary Swank, with a slightly British accent). An affair ensues. Meanwhile, Bucky has other secrets to keep, and ethical lines has been crossed. Kate (Scarlett Johansson) is attracted to him, even though she lives with Lee.