Zoë Lister

Through the 1950s and 1960s, and running alongside production of the gothic horror films, Hammer made a series of what were known as "mini-Hitchcocks" mostly scripted by Jimmy Sangster, and directed by Freddie Francis and Seth Holt. These low-budget suspense thrillers, often in black-and-white, typically had a twist at the end of the tale. [Wikipedia]

Val and her friends play a game that allows them to communicate with the dead. The Knock Knock Game turns any doorway into a portal to the hereafter, but the girls soon learn that there are rules that should never be broken.