Bite Me if You Can ~ Lynsay Sands

This is the fifth book in the Argeneau series. Lucian, the oldest member, and the backbone of the Argeneau family, is in Kansas City hunting down Morgan, an Immortal who has gone rogue. As He gets closer to destroying Morgan, he finds Leigh, a local restaurant owner, who Morgan has initiated the change on, but has not yet completed the change. Lucian ends up taking Leigh back to Toronto to complete the change, and discovers along the way that she is his lifemate, something he had given up on centuries earlier.