The Pain Hunter by Jeffery Deaver

A violent jailbreak bleeds into a street fair in Wisconsin. In the wake of the carnage, a getaway van barrels down a rural highway. Inside are two men with a tenuous bond: an obsession with pain.
One is Paul Offenbach, a sadistic crime boss with a life-threatening bullet wound. The other is his hostage, Dr. Stuart Collier, now faced with a harrowing ethical quandary. Mile by mile, as a calculated battle of wills and wits plays out, the killer plots his next move. So does the doctor, sworn to do no harm but desperate to escape.

From internationally bestselling master of suspense Jeffery Deaver comes The Pain Hunter, part of The Broken Doll collection, a series of interconnected short stories about killers and prey, justice and revenge, that can be read or listened to in a single breathless experience.