When strong-willed Summer Pratt takes a job at a beautiful estate as the new nanny to a sweet but sad little girl named Sophie, she soon starts to suspect something is very wrong with the beautiful, wealthy couple who call themselves her parents.

A single mother signs up for self-defense classes from a handsome instructor. But he develops a frightening obsession with her and orchestrates an increasing deadly array of “tests” to see if she has truly learned from his lessons.