Since she was found as a baby, floating in the Thames one foggy night, the webtoed Pearl has been brought up in a brothel known as the House of Mermaids. Cosseted and pampered there, it is only when her 14th birthday approaches that Pearl realises she is to be sold to the highest bidder. Meanwhile, the orphaned twins, Lily and Elijah, have shared an idyllic childhood, raised in a secluded country house with their grandfather. But when Lily and Elijah go on a visit to London, a chance meeting with Pearl will have repercussions for all of them, binding their fates together in a dark and dangerous way ...