El signo de los cuatro (Mi primer Sherlock Holmes)

My name is John Watson, I've just moved to London with my family, and this is the story of how I met my best friend, the amazing detective Sherlock Holmes. Together, we solve the trickiest and most mysterious cases on Baker Street, along with Toby, our loyal partner and the smartest and fastest bloodhound in the world. Case Notes: The Sign of Four An anonymous letter in a locker. A (very old) treasure map! What mystery lies behind the sign of four?