London is a city of secrets, but some secrets are too sick to stay hidden.

For centuries, the LineFolk—werecats, nymphs, and other creatures of myth—have survived in the shadows of the Underground, bound to the magical linether that keeps them human. But the fragile peace of the safezones is about to shatter.

When a young nymph collapses on the doorstep of the clynic, nurse Hannah Chadwick thinks she’s dealing with a simple human infection. She’s wrong. Within hours, the clynic is besieged by sick LineFolk, and the symptoms are as varied as they are terrifying.

As the mysterious plague spreads like wildfire across the Ouroboros, Hannah and Flynn must abandon their sanctuary for a makeshift field hospital in the heart of the City. But with resources dwindling and the body count rising, the abclynician’s dated Victorian methods are no longer enough.

With Detective Sergeant Patel torn between his duty to London and his feelings for Hannah, and a desperate Mia considering a bargain with her estranged, power-hungry father, the stakes have never been higher. If Hannah can't master her growing powers to find a cure, the LineFolk face two equally grim fates: total extinction, or a public exposure that will change London forever.

The LineFolk are failing. And the cure might be deadlier than the disease.