Bestselling author Katherine Webber pens a highly-anticipated and swoonful new spin-off to the Sunday Times bestselling YA romantic fantasy series, Twin Crowns.

Bursting with epic adventure, romance and humour on the high seas. Someone is making waves ...

Captain Marino Pegasi.

Wedded to the sea.

Immune to love.

Until now ...

Captain Marino Pegasi is never happier than when he's exploring the oceans. But when his beloved sister, Celeste, falls gravely ill, he is forced to go on a desperate search for a cure. Little does he know that in his search he will find so much more lying beyond the horizon. Does Marino's fate truly lie in the hands of a bewitching, mysterious mermaid ...?