"All Londoners will see what the Watchers are capable of on Christmas Eve ..."

December 1882. Attending the opening of the new Natural History Museum, Pall Mall Gazette reporter Alec Lonsdale and his colleague Hulda Friederichs are shocked to discover a body in the basement, hacked to death. Suspicion immediately falls on a trio of cannibals, brought over from the Congo as museum exhibits, who have disappeared without trace.

Alec however has his doubts - especially when he discovers that three other influential London men have been similarly murdered. When he and Hulda discover a letter in the victim's home warning of a catastrophic event planned for Christmas Eve, the pair find themselves in a race against time to discover who exactly the Watchers are and what it is they want ...