Ancient legend tells of an army of knights that will remain sleeping until the last days.

The knights are waking up.

A homeless man is stalked by a pale, wraithlike creature with a mouthful of needle-sharp teeth. Maimed animals and a host of suicides cluster around a mountain in Scotland. And deep beneath the cobbled streets of Oxford, a malicious hoard besieges a hidden city.

Freya Reynolds is a university student with a touch of OCD and an obsession with myth and folklore. Daniel Tully is living rough on the streets of Oxford, waging a...