The Grinning Man - S0.E3

At midnight on Midsummer's Day 1938, a famous Harvard geneticist, Eli Mencken, accepts a challenge to spend the night inside a gloomy old attic room... where the ghost of a madman is said to prey upon human flesh. Next morning, he has impossibly vanished from the hermetically sealed chamber. The only clue to his disappearance is traces of grisly ectoplasm on the bed.

Seventy years on, the vast Gothic house known as Metropolis has passed into the hands of the original owner's daughter and her son, but the strange, unexplained events in "The Nightmare Room" continue...