The Last 10 Seconds by Simon Kernick

When ex-police officer John Cone is found lying wounded in a room full of dead bodies, he has a terrifying story to tell.

Three days earlier he was hired by a mysterious client to snatch a suspected serial killer, Andrew Kent (aka the Penthouse Predator) from custody while he's being transferred between prisons. Kent is snatched, but then things immediately go wrong. People start dying, Kent goes missing, and Cone begins to realize that the case against him is not what he was led to believe.

Sharing that suspicion is newly promoted DI Tina Boyd, one of the murder squad team who arrested Kent several months earlier. But now Kent's disappeared, and Tina has to find him. And find him fast, because it's clear some very high-powered people want to silence him.