When a privately owned luxury yacht mysteriously explodes at sea, killing its wealthy owner, C. J. Hargrove, Robin Scott accepts an insurance company's assignment to investigate the circumstances surrounding the costly disaster. Through an unorthodox meeting with the deceased's daughter, Lydia Hargrove, her fiancé, Al Gilman, and her companion, Amy Wilde, Robin uncovers his first lead: a remark by Gilman that mentions the name Harmon. Following the lead, Robin locates Harmon and uncovers information linking him, Gilman, and Amy to the catastrophe. Moving quickly to counter Robin's investigation, the three nearly succeed in killing both him and Lydia. But Robin senses the truth in what others might dismiss as Lydia's insane ramblings. At the crucial moment, he devises a way out—one that brings Al Gilman and Amy to justice and costs Harmon his life.