Man Overboard!

Peculiar happenings aboard the schooner Helen B. Jackson when one night during a storm, the small crew found themselves diminished by one. Somebody had gone overboard, and it was surmised that it was one of the twin Benton brothers. But oddly enough, it seemed that the 'presence' of the missing twin continued to exist on board during the following weeks. For example, one extra set of silverware was found to be used after each meal, but nobody claimed to be using them. What then did happen that stormy night, and which brother, if indeed it was one of the brothers, was the man who went overboard?