Danny O'Neill hasn't had a single good night's sleep in the year since he discovered the book of storms. Exhausted and a social outcast, he wishes only to escape the shadowy figure of Sammael who controls his dreams and nightmares.

Cath Carrera, from the other side of town, dreams of escaping her brutish father and spiteful step-family. So when she meets Barshin, a talking hare who offers her protection from her dad's latest violent rage, she doesn't think twice about going with him. But she didn't expect to find a place like Chromos: a vibrant, addictive dreamland built from her imagination, in all its colours.

In return for his protection, Barshin wants Cath to deliver a message to Danny: he must rescue his cousin Tom from Sammael before it is too late.

Together, the three must find a way to stop Sammael before he destroys Tom. But even with the help of talking plants and creatures, and a friendly stag, the journey to Chromos and beyond is a dangerous, near-impossible mission, and Danny and Cath will have to muster every scrap of bravery and ingenuity to have a hope of succeeding.