William de Meton is gone; the demon spirit that drove Richard Thompson and his friends to take down the corrupt organisation OBS Ltd has abandoned them without direction or guidance. Left to fend for themselves, the group sets out to begin its own Order to carry on the work of the former witch-hunters.
Guided by an unseen entity and unbeknownst to her friends, Misty seeks to regain the knowledge lost through William's departure by invoking a restless spirit, unwittingly raising a parasitic demon far beyond her control.
As the creature calling itself Serus races to unleash its pestilence upon the world, Richard, Alex, Misty and Justin must fight to save thousands of infected innocents, before they too become victims of the Great Swarm...