Lettera H tells the story of Patty "Todaro" and Seba "Aceti". They love each other, despite the age difference. Seba is 37 years old, with a past made of petty crimes, and with Patty they share a passion for vintage 80's. Patty, to celebrate Seba's upcoming birthday, organizes a theme party with her closest friends. For the occasion, Seba has polished with great love a second-hand FIAT 127, a super mini car bought at a court auction. It's a seemingly perfect evening, everything goes as it should. At the end of the party, the two protagonists are secluded in a wood outside the city and, in the dark, as the anguish begins to rise, they feel observed by someone or something evil.
