Tilly and Tyler have been through it all together: acne and bad haircuts, school detention, sun poison during spring breaks, and family tragedies. He has been her support system, and she’s been his right-hand gal, and now he’s engaged to someone else. After a whirlwind romance with the petite and annoyingly sunny Sarah, Tyler is getting married and wants Tilly to be his Best Woman. She agrees, and even gets roped into helping plan the wedding, but is only doing so to break Sarah and Tyler up. Tilly recruits Sarah’s ex-boyfriend, Zack, to help in her plot, but the more she tries to interfere in the nuptials, the more she inadvertently helps Sarah and Tyler while becoming closer with the broody and surprisingly deep, Zack. Weaving a web of lies isn’t easy, facing the truth of a changing friendship is even harder. In the end, Tilly must be honest with herself, with Tyler, and with Zack about just how far she’s willing to go to break up her best friend’s wedding.