After leaving naval service to the British Crown, Captain Barton returns to his native Dublin. His life proceeds calmly and steadily, and a forty-year-old captain is now expected to marry a young and beautiful Miss Montague. Everything would be fine, but Barton begins to be followed by a mysterious “Watcher.” It trails him everywhere like an invisible shadow and sends threatening letters. The answer to the question “who is this tormentor?” lies in the captain’s distant past.