Casey (
Spencer Bradley) and her spouse, Shane (
Lucas Frost), are eagerly awaiting the arrival of Shane's stepmother, Marilyn (
Jennifer White). Shane is thrilled at the prospect of seeing his stepmom, while Casey, conversely, is a tad apprehensive. Casey confesses that she feels Marilyn harbors a dislike towards her.
Whenever they share a room, Marilyn always appears to be vying with Casey for Shane's attention. Shane reassures Casey that it isn't the case and suggests more time spent together might help, which is why he's pleased about Marilyn's impending visit. Despite Shane's reassurances, Casey remains skeptical.
Before she can voice her concerns further, Marilyn arrives, hauling her luggage through the entrance and welcoming Shane with a lip-lock. Casey is startled by this display but doesn't bring it up. While Marilyn clearly has a soft spot for Shane, it's evident she holds no affection for Casey, giving her a frosty reception.
In the ensuing days, Casey stumbles upon Shane and Marilyn in a number of seemingly amorous scenarios that give her pause. The first instance sees Casey overhearing Marilyn whispering secretively to Shane while throwing mocking looks her way. Shane dismisses it as mere dinner plans, and Casey lets it slide.
The second time, Casey spies Marilyn appreciating Shane's physique but doesn't confront them. However, the third time, when she catches them engaged in a sensual embrace on the couch, she can't keep her silence anymore. 'What the HELL is going on?' she demands.
Shane separates from his stepmom, his face etched with a pained expression of guilt. Marilyn, conversely, feels no need to conceal anything and boldly proclaims her sexual involvement with Shane. This revelation leaves Casey dumbfounded - it's too much to process.
How could Shane betray her like this? Shane confesses that he attempted to end it after marrying Casey, but he's powerless against his desires whenever Marilyn is around. He admits that his love for Casey and his inability to resist this forbidden temptation torment him. Processing this revelation, Casey concludes that irrespective of her actions, Shane will inevitably be drawn back to Marilyn.
If she can't rival Marilyn, then perhaps she can participate in their erotic escapades. Marilyn is initially reticent, but upon Casey's earnest plea for inclusion, she relents. They engage in a passionate threesome, with Casey striving to salvage her marriage from Marilyn's controlling influence.