Sherlock: Sign of Four

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 n...