It soon becomes clear that the plane was taken down by a rare, stolen machine gun. The list of people who could operate the weapon is short. And time runs even shorter.

But this isn't the only case the pair must solve. They're also tracking a serial killer who's ambushing young men in what the media are calling the 'Dead Hours' murders. With two killers and two different motives, Cross and Sampson are in a deadly race against time.