Famed stage actress Adriana Roman (Lana Turner) announces to the audience attending her final night of a successful run that she is giving up the life of an actress to marry her fiancé, rich entrepreneur Charles Winthrop (Dan O'Herlihy). Charles has a daughter from a previous marriage, Lisa (Karin Mossberg), and she is at this moment falling in with the wrong crowd as her uninhibited friend Bibi (Pamela Rodgers) introduces her to Johnny Allen (George Chakiris), a medical student who abuses the chemicals he is brought into contact with through his studies. Yes, Johnny is a prime source for LSD, and he's happy to hand it out to his far out friends - but then he sees an opportunity for the drug to make him serious money...
In the latter half of her career, on screen as in life, Lana Turner didn't have much luck with her daughters, or stepdaughter as Lisa was here. Adriana really makes an enemy of her, despite being fond of her because she resembles her so - in her own mind at least because there's a notable difference between these glamorous blondes, and it's not just the age. So: where did Lisa get her Swedish accent from? Her father doesn't have one, he sounds upper class American at a stretch, so why does Lisa speak as if she should be in an Ingmar Bergman film?
It's the movie's biggest mystery and it's never explained, never mind how she ended up in Mexico where this film was shot, but Mossberg didn't progress beyond the starlet role here, and remains distinctly non-famous perhaps because of The Big Cube's general ridiculousness. It's like a nineteen-sixties version of the kind of plot that might have turned up on TV in Dynasty fifteen years later, and Lana even gets her own soft-focus closeups much beloved of Joan Collins and Linda Evans. The premier gimmick utilised here is that fact that it has an ageing star tripping out on acid - well, acting that way at any rate, I don't know how much research or method acting Lana did for the role.
To put Adriana through such wigged out scenes she must first lose her husband, which she does when a yachting trip (not that kind of trip) goes horribly wrong. Previously, Lisa has raised the ire of her father when she brought home her new acquaintances and he walked in on Bibi whipping off her clothes for the benefit of the watching blokes, both in the film and in the audience. Such risque entertainment is not on in the Winthrop household, and despite Johnny trying to pour oil on the troubled waters, Charles is having none of it. This could throw a spanner into the works of Johnny's plans to marry Lisa for her fortune, especially having just been kicked out of medical school, but then his luck changes.
Now that Charles is missing presumed dead, the inheritance goes to Lisa and Adriana, with Adriana holding approval over who Lisa marries. Charles wouldn't have wanted his daughter marrying Johnny, so Adriana follows his wishes leading Johnny to hatch a new scheme: drug her sedatives with LSD and have her either committed or bumped off, whatever he can get away with. This is essentially another "drive the pure of heart heroine mad" tale, except in these troubled times it's the younger generation driving the older to insanity. It'll take the playwriting powers of Adriana's secret admirer Frederick (Richard Egan) to help her recover in an absurd development, but no more absurd than the rest of the film. Now fearsomely dated, The Big Cube is at its best as camp as only that "we want you to take this very seriously" style can be. Music by Val Johns.