The TARDIS brings the Doctor and Martha to Balmoral in 1902. Here they meet Captain Harry Carruthers - friend of the new king, Edward VII. Together they head for the castle to see the king - only to find that Balmoral Castle is gone, leaving just a hole in the ground. The Doctor realises it is the work of the Judoon - a race of ruthless intergalactic mercenary space police.
While Martha and Carruthers seek answers in London, the Doctor finds himself in what should be the most deserted place on Earth - and he is not alone.
With help from Arthur Conan Doyle, the Doctor and his friends discover a plot to take over the world. With time running out, who will fall victim to the revenge of the Judoon?
Featuring the tenth Doctor and Martha as played by David Tennant and Freema Agyeman in the acclaimed hit Doctor Who series from BBC Television.