Soul Deep - Dark Souls, #2

For nearly two centuries, Marcus has been the Watchers' most dedicated soldier. Sworn to protect humanity, driven by honor and a desire to atone for past sins, he's never questioned his mission or defied his leader. His partner, Regan, is the exact opposite. Her smart mouth and tender heart have fascinated Marcus for ages, but the Watchers' strict vow of celibacy has compelled him to ignore the sizzling attraction between them.
Until now. When Regan goes rogue to protect a very special little boy, Marcus is forced to make an impossible choice-commit an act of treason or watch the woman he secretly loves die. Hunted by enemies and allies alike, Regan and Marcus must fight to thwart an age-old prophecy and guard a boy who may very well hold the key to their past. A boy whose destiny is either to destroy the world.or save it.