“The devil who grants wishes…” is all that remains from the past in the memory of Valera Prishibleny. A tangled investigation leads the “Two-Faced” to the most mysterious place in St. Petersburg— the Rotunda on Gorokhovaya, where there is a staircase down which, at midnight, descends the devil, and under the dome an entrance to the fourth dimension opens. There, young detectives found a message. But the answer was given not by the king of darkness—rather by a person who even in the last moments of his life devoted himself to good.