I first saw this film as a child but its images haunted me for many years. This terrifying film has rarely been broadcast since, but was recently shown on American Movie Classics and I found it as frightening as I remembered. It is notable for the performance of the legendary acting teacher, Uta Hagen, whose film and TV appearances are limited but whose teachings are highly regarded in the acting world. Her role as Ada, the Russian grandmother of mysterious twin boys with a terrible secret, is perhaps not one of the great roles in film history, but her performance lends the film a tragic depth which makes the events seem all the more horrible. TV's John Ritter also has a small but important role as another member of the family beset by crises and dire events. And the late Portia Nelson, one of the nuns from THE SOUND OF MUSIC, also makes an appearance. Like many horror films of the 70's, this film sets a child's innocence against a malevolent force but, unlike The Exorcist or The Omen, doesn't involve supernatural elements. The horror is almost entirely psychological and involves the twins' relationship and a grief-stricken family. It would be foolish to give away too many details because the plot twists and shocking ending are so effective, but this film, without explicit violence or gore manages, to make an impact and is a must-see for horror fans.