The day after he turns thirteen, orphan Jax Aubrey awakes to a world without people. His reaction? It must be the zombie apocalypse. When everything goes back to normal the next day, he's sure he's lost it. Then Riley Pendare, Jax's eighteen-year-old guardian, breaks the news: yesterday was the Eighth Day, an extra twenty-four hours between Wednesday and Thursday. "Transitioners," like Jax and Riley, live in all eight days. Others, like Evangeline, the teenage girl who's been hiding in the house next door, exist only on this special day. The thrill of having a secret day wears off when Jax discovers Evangeline is being hunted by people who want to use her to eliminate the seven-day world--and everyone who lives there.