On His Watch by Susanne Matthews

You can’t outrun the past.

On leave from the FBI, Special Agent Jason Spark is enjoying some welcome peace and quiet when he’s called on to help the local sheriff’s department check out a 911 call. Expecting a prank or misdial, he unwittingly steps into a horrifying bloodbath straight out of a Hollywood slasher movie, complete with clues scrawled on the wall.
Nikki Hart’s husband and son are killed, but she survives, badly beaten and barely clinging to life in a coma. When she awakens, she doesn’t know her name, recognize her face, or remember anything about herself and her past. Terrified, and unsure of whom to trust, she clings to the memory of the angel who comforted her in her darkest moments.
The investigation turns up a prime suspect: The Butcher, an elusive hired assassin for the Sicilian mob. As the news of Nikki’s recovery spreads, putting her in this ruthless killer’s sights again, Jason will do whatever it takes to protect the woman he’s learning to love.

Nikki’s beginning to believe Jason might be the angel who protected her in her dreams. But when she learns about the secret role he played in the worst day of her life, can she ever forgive him?