Silas is a rag-and-bone boy, a ragamuffin who makes his living by scavenging in the dirty streets of the city and beachcombing by the wild blue sea. Early one morning, after a big storm, he makes greatest find of his life- a mermaid, a savage girl with a tail and claws,lying injured on the beach. Silas offers the mermaid shelter and protection. But Silas is only a ragged boy, and there are ruthless villains at large- ruffians who lurk in gangs in the twisting alleys, and who know that a mermaid could bring them fortunes beyond their wildest dreams...