In 1986, Eddie and his band of misfit friends are on the verge of adolescence. Bonded by mutual awkwardness and a yearning for excitement, they spend their days biking around their English village looking for adventure. The chalk men are their secret code, little chalk stick figures they draw for each other as hidden messages, warning of bullies or signifying meeting spots. But one morning Eddie finds a chalk man directing him into the nearby woods. He follows the message, only to find the dismembered body of a teenage girl. That is the day when everything changes. In 2016, Eddie is a grown man, working as a teacher at his old school, nursing a drinking problem, and trying to forget his past, until one day he gets a letter with no return address, containing a single chalk stick figure -- the same figure he saw the day he found the body. Soon he discovers that each of his old friends has received the same mysterious note. At first they brush it off as a bad prank, but when one of them is killed, Eddie realizes that saving himself means finally figuring out what really happened all those years ago. But digging into the past proves more dangerous than he could have imagined. Because in this town, everyone has secrets, no one is truly innocent, and some will do anything to keep the truth buried.