Sherlock, The Final Problem

Scotland Yard is baffled by a criminal defacing images of Margaret Thatcher, and Sherlock is convinced there is a more sinister purpose behind these acts of vandalism.

The sleuth faces a powerful new enemy who is seemingly unassailable, but who is concealing a terrible secret. Toby Jones guest stars as the villainous Culverton Smith.

The sleuth and Watson face their greatest challenge, as long-buried secrets catch up with them and a threat from the past seems to have returned from the dead.