From 1976 to 1977, four children outside of Detroit were abducted, held in captivity, and murdered. You Know They Know chronicles this allegedly-unsolved serial case known as the Oakland County Child Killings, now the subject of the TV show, Children of the Snow (Hulu, 2019), inspired by host J. Reuben Appelman's true-crime book, The Kill Jar (Simon & Schuster, 2018).