The Harrington sisters have never gotten along. Sara is a Type-A, career-focused event planner, and her younger sister Mariel is the opposite: bohemian, semi-employed, and recently engaged. When Sara's mother lures her back to Connecticut under false pretenses, she is perturbed to discover Mariel waiting for her, eager to reconcile their relationship -- and get some help with the final arrangements before her big day. The two sisters haven't spoken since the night Sara realized something was going on between Mariel and Sara's boyfriend, Carter Pryce. And now Mariel is about to marry Carter, the man she stole from Sara, the man Sara still loves. When Mariel asks Sara to stand in for a bridesmaid who has to cancel at the last minute, Sara realizes it's the perfect cover to unravel the nuptials and win Carter back. Sara begins to slowly sabotage Mariel's picture-perfect wedding, but when she crosses paths with David Cole, he challenges her self-image as the jilted second-fiddle to her spotlight-stealing sister. Will Sara realize what a bridesmaid-zilla she's become in time to fix the damage before Mariel's big day?