The Hartigan Browne Detective Agency has been contacted by London's Secret, Secret Service (so secret, that even the Secret Service doesn't know about them) to help locate the whereabouts of a missing agent who was in possession of the top secret object known only as the Silver Cipher. Finding the cipher is a matter of national security, and will take detectives through London as they track clues that will lead them to famous landmarks such as the London Eye, Trafalgar Square, the Natural History Museum and Buckingham Palace. Only those detectives with excellent brains and superior logic skills will be successful in solving the case of The Silver Cipher.