It's bad enough that Emma Porter lives alone with her mental illness. But things take a turn for the worse when her ex invites her to his book signing - for a best-seller whose plot she claims he stole from her - and on the way home she almost hits a woman with her car.

Star Marlowe. Beautiful. Fearless. Wild. Three things Emma is not. Emma is swept up in a new life of reckless adventure. She's happy and validated for the first time in years. But when Star exhibits more and more dangerous behavior, Emma starts to pull away.

Then, she gets a call: her ex has gone missing.

Emma thinks Star is behind it. The police think otherwise. Emma is arrested and confined to a psychiatric ward for a crime she didn't commit. No one believes her. What's worse, no one believes that Star is real. Desperate, Emma breaks out, determined to vindicate herself by finding the woman responsible – a woman who doesn't seem to exist at all.