The Altered's Atonement (Wolves of Stone Ridge, #58)

When Corporal Brian Haas took in a fellow marine's comatose younger brother in an attempt to figure out how to heal him, he never could have imagined the chain of events that it would set off. The testing his patient?Bailey Dyer?had been forcibly subjected to changed his DNA. Bailey had ended up turning into a paranormal creature called a shifter, giving him the ability to turn into a sentient cheetah at will.

Upon learning of shifters' existence, Brian agrees to relocate to the mountains of Colorado to help his buddy and the shifters looking into those targeting them. He builds a new bunker, preparing for when the thugs of the shadow military branch come calling. Brian knows it's just a matter of time, and he has every intention of making sure he and his new friends will be ready for them.

Brian spots a cheetah trotting into his yard. Assuming it's Bailey, he doesn't think anything about it...until it starts purring and rubbing up against him. This cheetah is not his ex-patient. When the man shifts, Brian finds himself face-to-face with a blond calling himself David Preston, and he seems to be just as confused by his sudden infatuation as Brian...until David calls Brian his mate.

Brian realizes his life is about to be turned upside-down all over again...if the confused altered can come to grips with his own changes.