Mario Bava’s final feature can be read as a ghost story or a film about a woman’s mental breakdown.

Either way it’s a highly distressing experience, Bava tightening the screws even as he unhinges all logic – the closing 20 minutes are excruciatingly tense and boast the most perfectly timed jump sequence in horror.

It was written by son Lamberto Bava and Dardano Sacchetti. “We wanted to do more of a contemporary horror film. We were influenced by Stephen King,” says Bava Jr, who also directed a handful of scenes.

It sees a mother and son return to the family home where dad committed suicide.  The kid goes all Danny-in-The Shining, mom (Daria Nicolodi) goes totally loopy and shit goes very strange, courtesy of some ingenious practical effects.

Bava made better films, more artistic films, but Shock – his most atypical horror film – is his scariest.

Argh! Can’t give away that jump scene so let’s go for Nicolodi lying on the bed with her hair swirling about her. Unnerving.

Remake rights: JA Bayona. The Orphanage owes Shock a lot.