was being built to interfere with the new Coastal Radar Station. The Hardy boys trap the criminals, including Cadmus Quill, in the cave while the State Police enter from the other end and arrest them all. The Navy is alerted and intercepts the submarine to find Morgan Todd being held hostage. Additional formats The revised edition was used for an episode of the Hardy Boys animated series and a View Master version also exists. References 1929 American novels The Hardy Boys books 1965 American novels Grosset & Dunlap books Submarines in fiction 1928 children's books 1965 children's books