1837. The Ohio River. May Bedloe is a seamstress to her cousin, the flamboyant actress Comfort Virtue. When they board the doomed Moselle their paths cross with Mrs Flora Howard, a wealthy abolitionist and notorious opportunist. Mrs Howard is quick to lure Comfort to her cause – a cause, it seems, that has no use for quiet little May. Casting out on her own for the first time, May lands a job on Hugo Cushin's wondrous Floating Theatre – a flatboat that sails the Ohio performing plays to the townsfolk along the way. Though shy at first, May quickly finds herself drawn into the eccentric troupe of characters aboard her new home: to sanctimonious, haughty Mrs Niffen and her browbeaten husband; to kind and gentle Leo, who steers the theatre from one riverbank town to the next; to sweet, open-hearted Liddy; and most of all, to the inscrutable Hugo himself. As the boat drifts south down the river, May gradually learns what it means to belong on her own terms, and how to fashion a family of sorts from this ragtag bunch of players. But just as May's new life is beginning to take shape around her, the reappearance of Comfort and Mrs Howard threatens to throw everything off course. To repay an old debt, May is not only compelled to break the law but also to guard a secret which puts the fate of the whole theatre – and all her hopes for a happy future – at risk ...