A patient with strange symptoms is admitted to a private clinic owned by the Zaslon company - under the influence of sunlight he becomes a bloodthirsty psychopath. An experimental method of wave therapy is applied to him, but “something goes wrong,” and the quarantine lockdown isolates the clinic from the outside world. The disease is spreading like a fire in a dry forest, the number of infected killer madmen is growing rapidly, and the doctor and the Zaslonov engineer have only seventy-two hours to stop the epidemic, otherwise the clinic will be wiped off the face of the earth.