When a mysterious chess problem in a London newspaper catches their attention, the young Sherlock Holmes, Arsene Lupin, and Irene Adler are on the case. The next day, a wealthy merchant is found murdered in his home, and on his desk was a scarlet rose - the calling card for the group of brazen criminals who wreaked havoc on the city twenty years ago. Can the three young investigators solve the code before the Scarlet Rose Gang completes another murder?