Solomonsky Circus on Tsvetnoy Boulevard is preparing a New Year's performance. The show promises to be unforgettable - a new twentieth century is on the verge! But there was a commotion in the circus backstage: someone drew a skull and bones on the poster... This sign - like a black mark - does not bode well. The illusionist Gambrini accuses the famous trainer Vladimir Durov of what happened. Gilyarovsky decides to stand up for his friend and unravel this case. Durov tells him a long-standing story about a series of mysterious deaths that occurred in the circus right in the arena. Each of them was preceded by an already well-known symbol - a skull and bones. But who is he - this evil clown who arranged a truly deadly number?