Falling from the balcony of one of the Moscow houses, a young girl Ekaterina Averkina crashed to death. Many neighbors who were walking in the yard at that moment saw Katya pushed down by her older sister Natasha. She is immediately arrested. The girl is shocked - during the tragedy she... walked around Moscow with her young man Lenar! But it is impossible to prove this - the testimony crosses out all Natasha's arguments, and it seems that nothing can help her. However, lawyer Vitaly Kirgan and detective Anton Stashis became interested in the case of Averkina Sr. In the course of the investigation, they discover unexpected facts that will eventually lead them to a stunning clue...