Shadows - Season 1 - Eps 5: An Optical Illusion
Three teenagers tour a spooky old Tudor mansion just before it's about to close for the night. They hide in a secret passageway and get locked in.
About Shadows

Title: Shadows
First Air Date: 1975-09-03
Last Air Date: 1978-11-01
Status: Ended
Rating: 5.7/10 (from 3 votes)
Language: EN
Seasons: 3
Total Episodes: 20
Network: ITV1
Genres: Drama
Production Companies: Unknown
Synopsis
Shadows is a British Supernatural television anthology series produced by Thames Television for ITV between 1975 and 1978. Extending over three seasons, it featured ghost and horror dramas for children. Guest actors included John Nettleton, Gareth Thomas, Jenny Agutter, Pauline Quirke, Brian Glover, June Brown, Rachel Herbert, Jacqueline Pearce and Gwyneth Strong. The series was also notable for reviving the character of Mr. Stabs. Notable writers for the series included J. B. Priestley, Fay Weldon and PJ Hammond.