Deadly Lover by Jocelynn Drake

Justin Mallory has years of bad decisions to make up for, starting with agreeing to join the CIA after being recruited out of the Marines. Now he chooses the jobs and he works alone. It’s safer that way, and he can make sure the good guy always wins.
But this job…he can’t do alone. Two pharmaceutical researchers are dead and a dangerous drug is on the cusp of winning FDA approval if he doesn’t track down the culprit behind the lies and murders.
Gabriel Prescott is a well-trained, efficient, and cold-blooded killer. After a brutal betrayal left his lover dead, Gabriel is out only for himself. But when this lucrative contract lands in his lap, he can’t pass it up. Even if it means working with the unpredictable and insane Justin Mallory.
Dodging bullets and secret meetings find them depending on each other. And one hot, frantic night together leads to a hidden sweetness…and questions of whether they could possibly have something more.