The voice-over goon is more interested in hyping "Fantastic Horror Vision" than actually telling you anything about the movie, which is a shame.  The "Horror Vision" consisted of a chap in a gorilla suit running into the audience and making off with an actress planted in the cinema, who then 'magically' appear on the screen.

So, plotwise, some girls decide to spend the night in a haunted house, where they are abducted by a crazed scientist and his pasty-faced accomplice, and one of the girls is turned into a very unconvincing gorilla.  Groooooovy.

Incidentally, none of the girls are actually wearing pyjamas.  BLATANT FALSE ADVERTISING.

Favourite bit:  The gorilla's act when it wakes up on the table.