Valentine's Day is approaching. Lila and her classmates are going to a party, not even realizing that in a few moments a single letter will turn their cheerful student life upside down. Just a couple of lines for one of Lila’s friends – Sonny. “Your heart will be mine”... What is this? A love letter from a secret admirer? Threat? No, just a stupid prank! But soon after the letter appears, Sonny disappears without a trace, and then a new message arrives: “Your turn!”