The hit BBC series Sherlock, starring Benedict Cumberbatch, offers a fresh, contemporary take on the original Sir Arthur Conan Doyle stories, and has helped introduce a whole new generation of fans to the legendary detective. In this TV tie-in edition to the classic novel, Sherlock and Dr Watson receive a visit from Mary Morsten, who offers up a particularly cryptic puzzle for them to solve.

Her father went missing six years ago and since then she has received a pearl for every year he has not re-appeared.

Now, the treasure's sender has requested a meeting and she would like Sherlock and Watson to accompany her.

Finding the mystery benefactor is only the start of this adventure, that puts Sherlock and Watson hot on the trail of cold-blooded killers and thieves, and a lost Indian fortune.