The Whisperer in Darkness

For the first Act structure, the plot follows the short story. In the third act, the protagonist, Wilmarth, uncovers an attempt by cultists to open a gateway between Yuggoth and Earth. He foils the plot with the help of Hannah, the child of one of the collaborators. His escape is unsuccessful and at the end of the film the audience discovers that Wilmarth has been narrating from a machine attached to the cylinder in which his brain now resides. This differs from the original story in which Wilmarth flees in the middle of the night and safely returns to Arkham.