Phantom Shadows by Dianne Duvall

Dr. Melanie Lipton is no stranger to the supernatural. She knows immortals better than they know themselves, right down to their stubborn little genes. So although a handsome rogue immortal seems suspicious to her colleagues, Sebastien Newcombe intrigues Melanie. His history is checkered, his scars are impressive, and his ideas are daring. But it’s not his ideas that have Melanie fighting off surges of desire . . .

Bastien is used to being the bad guy. In fact, he can’t remember the last time he had an ally he could trust. But Melanie is different — and under her calm, professional exterior he senses a passion beyond anything in his centuries of experience. Giving in to temptation is out of the question — he can’t put her in danger. But she isn’t asking him . . .