Louise (Luana Anders) is married to John Haloran (Peter Read), and wants to get her hands on his mother's inheritance. However, John has a heart condition and Louise will only be rich if he still lives; so how unfortunate it is when they are out rowing on the bay near the Haloran estate in Ireland that after an exchange of bitter comments with his wife, John has the much dreaded heart attack. Louise searches his pockets for his pills, yet he's run out of them and she tries to frantically row back to shore - but it's too late and John has died. What to do? Dump the body over the side, of course, and pretend he's still alive...
This atmospheric shocker has its own small place in movie history as the first legitimate film to carry Francis Ford Coppola's directorial credit (I guess he'd rather forget about the nudie flicks he made beforehand). He also wrote the script, and seized his chance when producer Roger Corman was working on The Young Racers in Ireland and gave his assistant part of the budget and some of the cast of that film to make his own. The result mixed the twists of Psycho with the axe murders of Strait-Jacket, and cult fans will be interested to see Jack Hill listed as Coppola's asssitant director here.
But Dementia 13 has a Gothic mood all its own, and is interesting for having the treacherous Louise as its anti-heroine to guide us through the over-involved plotting. She types up a letter to Lady Haloran (Eithne Dunne) pretending that John has gone back home on a business engagement, and takes her place at the dinner table as if nothing is wrong. John has two brothers, Billy (Bart Patton) and Richard (William Campbell) who must take part in a ceremony held every year with their mother on a particularly fateful anniversary.
The anniversary is of the death of their younger sister, Kathleen, who Lady Haloran remains in deep mourning for. She died in mysterious circumstances in an apparent drowning accident, and when the ceremony goes ahead, with Louise watching from the parapets of the castle, Lady Haloran abruptly faints. Louise rushes down to find out what went wrong, only to be told that the flowers placed on the grave have suddenly died. Louise sees an opportunity to secure the inheritance by playing on her mother-in-law's superstitions, so hatches a plan involving placing Kathleen's toys at the bottom of the pond where they can float up during the day in an apparently supernatural manner.
And so begins Dementia 13's most famous sequence, an early sign of the talent of this director, with Anders stripping down to her underwear to dive into the pond during the night. What Louise finds shocks her, but not half as much as what shocks her when she surfaces. There are only two real suspects as to who the real villain is, and one of them is the victim of a bunch of red herrings so obvious you probably won't be taken aback by the ending, but the journey to get there is a creepy one, complete with spooky toys twenty years before Poltergeist. And there's the bonus of Patrick Magee showing up as the local doctor turned detective who is determined in his eccentric manner to get to the source of the mystery. All in all, this effort was an impressive way for Coppola to really arrive on the movie scene. Music by Ronald Stein.