Amateur sleuth Queen Elizabeth II investigates on the high seas in the sixth installment of this historical mystery series the New York Times Book Review calls "sheer entertainment," perfect for fans of Rhys Bowen and Richard Osman.

1966, Caribbean Sea. The Queen is touring the islands of the West Indies aboard the Royal Yacht Britannia. Her schedule is packed with official visits, but when her new diary secretary, young Pamela Sinclair, is found dead in her cabin, the whole trip threatens to be thrown off course.

Pamela's death from an overdose of prescription pills is surrounded by details that don't add up. It looks as though she was afraid of someone on board, and Joan McGraw—the Queen's loyal sidekick and assistant private secretary—is the leading suspect.

With the whole world watching, the real circumstances surrounding her death must be uncovered, and quickly. Luckily for the Queen, she and Joan are experts at floating from one engagement to the next as the tour continues and the killer roams free—for now.