After discovering that Caitlin tricked Tony into marriage by faking a pregnancy, Abigail and Parker infiltrate the wedding party as "undercover" bridesmaids. Their mission is to sabotage the wedding from the inside and reunite Tony with their heartbroken friend, Rachel.
They kidnap Caitlin on her wedding day to force a pregnancy test. While she refuses the test, she accidentally confesses she is only marrying Tony for money, unaware she is being recorded.
The central plot focuses on the extreme lengths friends will go to protect one another from manipulation.
While the bridesmaids use "iffy" methods like destruction of property and kidnapping, the film frames their actions as a quest for "true love" and standing up to childhood bullies.