December, 1799. Europe is recovering from the Age or Reason, the Vatican is learning to live with Napoleon, and America is celebrating a new era of independence. But in New York State, something is spreading its own brand of madness through the streets. Secret societies are crawling from the woodwork, and there’s a Satanic conspiracy around every corner.

Roz Forrester is stranded in a town where festive cheer and random violence go hand-in-hand. Chris Cwej is trapped on board the TARDIS with someone who’s been trained to kill him. And when Reason itself breaks down, even the Doctor can’t be sure who or what he’s fighting for.