New York City is being attacked by a deadly killer that has a weapon to harness and steer electricity into huge arc flashes. When the first explosion occurs in broad daylight officials fear terrorism and Rhyme is immediately tapped for the investigation. Meanwhile, he's consulting on another high-profile investigation in Mexico regarding the Watchmaker, one of the few criminals to have eluded his net. Juggling two massive investigations against a cruel ticking clock takes a toll on Rhyme's health and his determination to work despite his physical limitations threatens to drive away his closest allies when he needs them most.