Fog can hide evil deeds and fogs invade East Anglia all of the time. In the ancient village of Upper Heath stands the remains of Old Church, raised during the Anarchy on even older ruins.

The tension rises through the year for a group of children, who battle the local thugs as well as the mysteries surrounding the ruins. They are helped by two priests and a police officer, and for them the horror appears in the disused American airfield. Phantom aircraft take off in the dead of night and ghostly figures are reported.

The final confrontation is between good and evil dating back centuries and involving surprising forces.