When Nancy’s friend Emily finds that some very precious inherited jewels are stolen, the mystery begins. The fourth book was almost again like two mysteries in one, not only about the stolen jewels but a mysterious ghost like figure leaving messages in the middle of the night

Nancy traces all the evidence back to a maid service who has employed various women who have helped out at the house. Soon Nancy finds herself in danger when a gang traps her in a sinking ship with the jewels and only a prayer that she will be able to escape.