Lured by the promise of a rare and elusive butterfly, the intrepid Veronica Speedwell is persuaded by Lord Templeton-Vane to pose as his fiancee at a house party on a Cornish isle owned by his oldest friend, Malcolm. But Veronica soon learns that one question hangs over the party: What happened to Rosamund, Malcolm's bride who disappeared on their wedding day? Now those who were closest to her have gathered, each a possible suspect in her disappearance, and Veronica is determined to uncover what happened - and potentially find a killer.