Aurora, Michigan is finally at peace for the first time in months. It doesn't last very long.
As Cal Kinsey is creeping up to his one-year anniversary on Riker's team, something else is creeping through the streets of Aurora. One by one, people are falling ill with severe flu-like symptoms, and the doctors are stumped, unsure of the cause. 
At first, the supernatural community ignores this largely human problem...until a wizard is infected and flies into an insane rage, destroying almost half a city block. 
That is when the truth comes out: It's not a disease at all. It's an infectious curse.
With Aurora's supernatural community descending into panic, DSI goes on high alert, and every team is mobilized to hunt down the curse's source. But the ICM refuses to cooperate with the investigation. Terrified practitioners try to flee the city, risking an epidemic. A scared witch attacks a DSI team, killing multiple agents.
And just when Cal and his teammates think it can't possibly get any worse, the unthinkable happens.
The new leader of the local ICM chapter accuses a DSI agent of playing a part in the creation of the curse. Specifically, he accuses one of DSI's elite detectives: the one and only Cal Kinsey.