Nancy investigates a small ship cottage at the Chatham estate and discovers a connection between the mysterious occurrences at the cottage and an island where a lost treasure is said to be buried. With one half of a map, Nancy sets out to find a missing twin brother who holds the other half. The mystery becomes dangerous when an assailant hears about the treasure and is determined to push Nancy off the trail. Can she endure this and other grave dangers, and recover in time to solve the mystery?

This eighteenth book in the Nancy Drew series was originally published in 1941.

The eighteen-year-old girl detective must find a man who has been missing for years in order to locate the other half of a treasure map.

Nancy becomes involved in a double mystery concerning a haunted bridge and jewel thieves.

Prompted by the concerns of a young child, Nancy investigates a small studio on the Chatham estate. She discovers that there is a connection between the mysterious occurrences at Ship Cottage and her search for a treasure island. With only half of a map, Nancy sets out to find the man who possess the rest of the map that will pinpoint the location of buried treasure. Constantly beset by danger and intrigue, Nancy courageously outwits her enemies and solves one of the most challenging cases in her career as a teenage investigator.

Nancy, Bess, and George encounter a troublesome stray terrier on their way to the opening festivities of a new park and recreation complex in River Heights. The terrier grabs the handbag of one of the guest speakers and loses it in a nearby pond. Nancy helps groundskeepers retrieve the handbag and uses the notes found inside to prompt the nervous speaker during her address. She also finds a mysterious personal ad in the handbag. In a casual observation, the "clubwoman," a Mrs. Owen, tells Nancy about a statue on a deserted seaside estate.

A friend of Carson Drew’s has been arrested and charged with sending a truck loaded with explosive oranges into the Space Center complex at Cape Kennedy. Knowing that Mr. Billington could not possibly be guilt of sabotage, Nancy and her father rush to the defense of the accused man. During the Drews’ investigation Nancy become suspicious of an old spooky mansion that houses fierce African wild animals on its extensive grounds. Soon, she discovers that something besides the training of wild animals is going on at the mysterious estate. Many dangerous moments await Nancy before she proves Mr. Billington’s innocence and thwarts the plans of treacherous subversives bent on undermining the U.S. space program.