Blood vow / J. R. Ward.

Trainees at the Black Dagger Brotherhood' training centre continue to prepare for the fight against the Lessening Society, but fighting is the last thing on Axe's mind. Still plagued with the guilt of his father's death, the brooding loner finds himself battling an unlikely attraction to Peyton's bright, aristocratic cousin, Elise. Elise feels it too - and when the two are thrown together in unusual circumstances Elise must decide whether she can trust Axe to help her uncover the mystery surrounding her sister's death. Meanwhile, Mary and Rhage are in the process of adopting Bitty, a young pretrans orphan, until the appearance of a young male claiming to be Bitty's blooded uncle threatens to tear the new family apart.