One of the best special effects you'll ever see

Imagine it. It's 1937. The world is rumbling towards another world war. You go to the cinema for a bit of fun. There's a wacky looking comedy thriller on called Sh! The Octopus. You think to yourself "this will be a laugh." Little do you know there's a scene in it near the end so creepy and brilliantly put together that 84 years later nerds will still be writing about it.

Two detectives on the hunt for an infamous criminal called the Octopus find themselves trapped on a stormy night in a lighthouse with a group of people and would you believe it, there's a real octopus out to kill them too. As the story comes to a climax this happens.

My god it's effective isn't it. Really unsettling. A real How the fuck did they do that? special effect. How the fuck did they do it anyway? Actress Elspeth Dudgeon's face and teeth were made up with red make up first and then the scene was lit with red light as the camera rolled. On black and white film the red make up was rendered invisible by the red light making her character Nanny appear normal looking. Then with exquisite timing, just as her wig is wrenched off revealing the ragged hair beneath, the red lighting is quickly switched to blue and the make shows up on film. But not the blue light as it's not visible in B&W. A very simple but stunningly effective technique. Much more elegant than any crappy CGI. The effect was created by a cinematographer called Karl Strauss and turned up in the silent film versions of Ben-Hur and Doctor Jekyll & Mr Hyde too but it was never showcased better than here. Of course Elspeth Dudgeon's performance really sold it too. Nothing like a wicked cackle to give you the chills.

Nope. The stuff of nightmares.