Barcelona, 1937. The Doctor has been trying to introduce Fitz and Anji to the vibrancy of pre-war culture, but anomalies in that culture are puzzling them all. How can Picasso's `Guernica' emanate both impassioned protest and clinical detachment at once? What really happened when the city was bombed?

There is a strange presence in 1930s Barcelona, determinedly twisting reality to a set pattern, desperately trying to make events make sense. Which, as the Doctor knows, is precisely what they don't tend to do. Not when you add human subjectivity into the equation.

As the observer becomes increasingly frantic in its manipulations of the timestream, everyone involved in the Spanish Civil War is affected. A certain Eric Blair finds himself using advanced torture techniques on his old anarchist comrades. The Doctor has to find it, and understand its deranged meddling, before it drags the whole of history into its madness.