Every other day, Kali D’Angelo is just a regular sixteen-year-old girl. She attends public high school, bickers with her dad, and leads a normal life as a human.

But on the alternate days, she transforms completely.

While she may still look like herself, every 24 hours her predatory instincts take over, turning her into a feared demon-hunter with an unyielding drive to hunt, trap, and eliminate zombies, hellhounds, and various supernatural threats. Kali doesn’t understand why this happens, but she succumbs to these instincts anyway, even though the government deems it as environmental terrorism.

When Kali spots a mark on the back of a popular classmate, she instantly knows the girl is destined to be killed by one of these creatures. With only 24 hours to save her, Kali must do so as a human, relying on the help of some new friends. She takes a dangerous risk, knowing her human body might not survive, all while uncovering the secrets behind her mysterious condition.