The main heroine of the book is Mariya Ivanovna. She owns a magical mirror-psyche that allows her to go back into the past: sometimes to be surprised, sometimes to laugh, and sometimes even to be afraid. The Soviet and post-Soviet time — the years when the girl Masha grew up — is refracted through this mirror. The reader can expect adventures of Masha, sometimes mystical oddities of the world of a child, a teenager, a girl who is convinced that in the mirror world lives her sister. Maybe not just one! Not only a sister either!