When you save your guardian angel.

Zandriel once a fierce Warrior angle had been tasked to protect a woman gifted with the "sight" But he failed and it cost the woman her life, driven by the burden of his failure Zandreil keeps an eye on the woman's grand-daughter. Cassandra had not yet realized how her life would change working what feels like a dead end job she has yet to discover the gift that lies in her blood line - that is until an angel appears in her life.
when heaven and hell both want to use Cassie for her powers, how far wll Zandriel go to keep her save ?
or will she have to save him from himself ?