After the tragic death of his daughter, Jack finds himself with more questions than answers. While reading his daughter's diary about an imaginary unicorn called Summer, he begins to suspect that the unicorn may not be so imaginary after all. Questioning his own sanity, he soon finds himself on a desperate search to unravel the mystery of the unicorn and find what really happened to his daughter. As answers come to light, he begins to regret what he finds, as mythology meets reality and the truth about unicorns becomes known.