Part-time librarian Molly Matthews lives with the painful and exhausting chronic illness ME. The condition has broken every part of her life, except that she has plenty of time to escape into books. Especially her favourite fantasy series, Tamass the Fearless. And when Molly escapes, she really escapes, because she possesses a rare talent that allows her to enter a book and meet its characters and share their adventures. Molly is a Storywalker. Novelist Paul Best doesn’t walk in stories, but he’s always been good at making them up. At least, that’s what he believes, until he learns that he’s spent years unconsciously channelling the life of his unknown twin brother Tamass as the hero of his successful series. When Tamass turns up at Paul’s door one dark and stormy night with murderous demons on his tail, it’s the start of a frantic multiverse-hopping adventure. And then there’s Molly, one of Paul’s readers, a woman who is so quietly ill in one world that she’s nearly invisible, but who is seen riding a warrior dragon in other worlds. A generation ago, the ruthless demon Baron Rake put an end to the snooping of Paul’s and Tamass’s parents into his plans to enslave the multiverse. He is furious when their sons and Molly pick up the investigation again just when he’s about to make his final move. Separately, and each with the help of friends old and new, Molly and Paul cross worlds that leak people, creatures, and mythologies back and forth, and their paths converge as they fight against impossible odds to save their entire multiverse.