Let Me In by Donna Kauffman

He's bringing anything but peace and quiet. Tate Winslow is done with all the guns, the adventures, the brushes with death. All she wants is to be left alone. So when her enigmatic ex-boss shows up on her doorstep barely alive, she really tries not to care. He's all alpha male, the baddest of the bad-and a threat to her hard-won peace in more ways than one.
Tate is the only lead Derek Cole has on a case that could blow the intelligence world apart-if it doesn't kill him before he can figure it out. She was his best agent, but she's in hiding and he's gone rogue, and he's starting to think of her in a very nonprofessional way. In fact, he wants Tate like he wants his next breath, but he's already risking his life and his career.does he need to put his heart in danger too?