The powers of good are pitted against the forces of evil as the Duc de Richelieu wrestles with the charming but deadly Satanist, Mocata, for the soul of his friend. Mocata has the knowledge and the power to summon the forces of darkness and, as the Duc de Richelieu and his friends remain within the protected pentacle, they are subjected to ever-increasing horror until thundering hooves herald the arrival of the Angel of Death.

While mainland Britain shivers in deepest winter, the northern island of Fara bakes in the nineties, and the boys at the Met station have no more idea what is going on than the regulars at the Swan. Only a stand-offish visting scientist realizes space aliens are to blame.