The Soul Keepers by G. P. Ching
When fifteen-year-old Jacob Lau is pulled from the crumpled remains of his mother's car, no one can explain why he was driving or why the police can't find his mother's body. Made a ward of his uncle and thousands of miles from home, a beautiful and mysterious neighbor, Dr. Abigail Silva, offers to use her unique abilities to help him find his mom. In exchange, she requires Jacob to train as a Soulkeeper, a gifted warrior charged with protecting human souls. He agrees to her demands, desperate for any clue to the mystery of his mother's disappearance. But soon Jacob finds himself trapped in a web of half-truths, and questions Dr. Silva's motives for helping him.