Amateur sleuths Jessie Harper and George Jenkins, of the Dale Street Private Investigations Agency, and Jessie's companion, the mysterious talking cat Khan set off on another murder investigation in 1930's Liverpool, England. Their old friend and mentor, Detective Sergeant Bill Roberts of the Liverpool City Police asks them to take on a cold case, a dockland murder with supernatural elements. They agree and start their own investigation just before the fifth anniversary of the murder on Christmas Eve. Their suspect is Jack Crawley, a rough dock worker with a quick temper and a history of violence. As they approach him, he denies knowing anything about the murder, but his nervousness suggests otherwise. Following Khan's lead, they investigate further and eventually uncover the truth behind the crime.