One ordinary boy named Timofey, thinking hard about solving the problem “from point A to point B,” suddenly found himself in a mysterious country ruled by Her Mathematical Majesty. He faces mortal danger at every turn, because he is wanted as a criminal, and Doctor Plus and Doctor Minus are hunting for him. They are able to read thoughts and severely punish disobedience and offenses, “neglecting” or “increasing”, which threatens death. But his friends help him: a boy who is desperately cowardly, but overcomes his fear, and an extraordinary girl, Her Arithmetic Ladyship, who fell in love very much music performed in his mind (after all, she also hears thoughts)...