After the tragic death of his wife, Richard Wynn (LINDEN ASHBY) is grateful when his sister-in-law, Laci Collins (LINDA PURL), volunteers to move in with him and help him care for his two children. However, Richard does not realize that Laci is emotionally disturbed and covets her late sister's life... and is secretly obsessed with Richard himself.
Two years later, when Richard announces that he is planning to get married to gorgeous Nicole Garvey (SHANNON STURGES), Laci is devastated. And when Nicole asks Laci to be her Maid of Honor... a gesture of appreciation for Laci's selfless devotion to the children... Laci secretly vows to do whatever she can to stop the wedding.
Laci digs into Nicole's past and discovers that Nicole has a painful secret... that she was married many years ago to an abusive man who went to jail for manslaughter. And so Laci concocts a devious plan: She contacts Nicole's ex-husband and convinces him to make an explosive phone call to Richard, which compels him to confront Nicole about the deception and forces him to consider calling off the wedding.
However, much to Laci's disappointment, Richard forgives Nicole. Now Laci has no choice but to take more drastic measures... she decides to buy a cake for Nicole's "bridal shower" laced with nuts, knowing that Nicole is deathly allergic. When Nicole eats the cake, she nearly dies, but is saved at the last minute by a diligent paramedic.
Laci decides to spend the night with Nicole at the hospital, intending to "finish the job" when no one is around. But Laci's niece Mollie has become suspicious of her and catches Laci in the act of trying to smother Nicole. The plucky teenager then tells her father everything, unmasking Laci's treachery and psychosis...
Laci flees the hospital and stands over a raging river, dropping her purse into the watery maelstrom below. The look on her face tells us that she has decided to end her life.
A few weeks later, Richard and Nicole have recovered from their ordeal, and, believing that Laci is dead, finally go through with the wedding. But unbeknownst to them, there is a mysterious presence watching them from the balcony of the church... Laci ! As Richard and Nicole head off to the mountains for their honeymoon, little do they realize that Laci is lying in wait... and that if she has it her way, this honeymoon will end in a funeral... for two.