Head Games by Onley James

“You’re a vigilante in an argyle sweater.”

Straight-laced psychologist Tobias is an expert in the deviant behavior of others but a novice when it comes to his latest endeavor: serial killer.
After years of high-profile kills and mentoring numerous other assassins, laid-back Soren lives his life in a state of semi-permanent vacation. He comes out of an early retirement to help out a friend, only to set off sparks with the renowned psychologist when they discover they’re hunting the same man.
One shaky truce and a whole lot of blood later, Soren has a new mentee in Tobias.
Soren finds Tobias and his dark impulses fascinating. Tobias finds Soren’s relaxed attitude infuriating. They have nothing in common except their ability to kill and chemistry neither can deny. But a kill list, a rage room, the Irish mob and the ghosts of their past all stand in the way of their happily ever after.