Ever-superstitious Alex Mills will do anything to avoid a jinx. Picking up pennies, knocking on wood, collecting rabbit's feet . . . you name it. That is until she steps on a crack and it actually does break her mother's back. To save her mom, Alex must follow Hubbub Caskside, a trusty leprechaun, on a journey through the end of a rainbow to Haphaven, the world where all of Earth's superstitions draw their power. All she needs is a rabbit's foot to save her mom, but she soon discovers the lucky article won't be so easy to retrieve. Not only is the rabbit's foot guarded by Haphaven's most formidable creature, the Jinx, there's also a forest full of trees that knock back if you don't knock on wood, people named Penny who do not like to be picked up, and a particularly vindictive black cat who will not be crossed.

As Alex finds herself desperately searching for a way to save her mom, she learns of a mysterious connection between her family's fate and the rulers of Haphaven. With her mother's life on the line and her own fate at stake, Alex must find the strength within herself to unlock the mystery and take back control of the superstitions that have controlled her life, even if it means crossing the Black Cat once and for all.