It's Christmas eve at 221B Baker Street. On the stroke of midnight, a delivery arrives addressed to Sherlock Holmes. The message is a cryptogram which reveals itself to be so obtuse that it has the famous consulting detective baffled. Holmes becomes so obsessed with revealing the secret of the cypher that Watson fears for his well-being in refusing to eat or sleep. Holmes can only deduce that time is of the essence, and that a means of deciphering must be discovered which has never before been employed. Watson wonders what new adventure will emerge should the puzzle be unraveled. Adaptation of the stage play of the same name.