American detective Grant Colwyn is on a leisurely holiday in a fashionable seaside hotel in Norfolk when one morning during breakfast the strange behavior of one of the other guests catches his attention. The young man's unusual conduct alarms other visitors as well - Colwyn suspects a severe case of a shell-shock. The guest is escorted to his bedroom with some help from Colwyn and Sir Henry Durwood, a doctor who happens to be staying at the hotel, but a few hours later the ill guest disappears without a trace. The next day a man of his description is accused of a murder, and Detective Colwyn...