Three die in a psychiatric hospital.

A triple homicide.

A contagion, deadly and mysterious, is the killer's weapon of choice.

A dart flies. A woman dies in the shower, her neck is punctured.

A homicide, hours from Chicago.

Poison, deadly and concocted, is the killer's weapon of choice.

As her city teeters on the verge of panic, Detective Rylee Hayes is forced to divide her attention between two killers, one whose actions could result in a global pandemic and the other, an old nemesis whose next target is her fiancée.

And the clock ticks precious time.