The title tells a lie: It's actually two bad sisters. The middle sibling Lorna (played by Sara Shane) proves as virtuous as she is dull, compared to the psychotic (Valerie, played by Kathleen Hughes) and the nymphomaniac (Vicki, played by Marla English) with whom she shares a mansion and their dead father's millions. (Also in the mix is a boozed-up busybody of an aunt played by Madge Kennedy.)
The trouble, which has been brewing for three lifetimes, boils over when dad dies in a plane crash. The pilot (John Bromfield) claims to have tried to save him, but doubts abound. Valerie, sniffing an opportunity, schemes to have him brought into the family business and marry him off to Lorna, engaged to the estate's executor (Jess Barker). She hadn't reckoned on Vicki, who throws herself at Bromfield as though lust had just been put on the market in easy-to-swallow caplets (`I graduated magna cum laude from Embraceable U,' she coos at him).
Valerie and Vicki make Goneril and Regan look like Little Sisters of the Poor. They openly and viciously taunt one another, and Lorna, about age, and looks, and anything else their stoat-like minds can come up with. In one eyes-like-saucers scene, the twisted sisters get into a cat-fight concluding with Valerie's taking a riding crop to Vicki's face, driving her (quite literally) around the bend. All the while she's photographed in pitiless close-up, her thickly-lipsticked maw stretched wide in ecstatic triumph. But wait! There's more....
Suds'd-up trash so pungent it's hard to pass it by, Three Bad Sisters was a late-50s Z-movie template for the motivelessly malignant soaps and serials that soon became a staple of television screens, filling the days of our lives. Script, acting and production boast no redeeming qualities whatsoever, except excess and sheer effrontery. In regard to those qualities, Three Bad Sisters offers an embarrassment of riches.