"Pretty Little Liars" is an American TV show based on a series of novels by Sara Shepard. It aired on the Freeform channel from 2010 to 2017. The plot revolves around four friends who come together after their mutual acquaintance mysteriously disappears. Soon, Alison's body is found by the police. However, even after her death, the main characters continue to receive mysterious messages containing their dirtiest and most secret secrets. The girls try their best to find the stranger who is sending them the letters.