Sarah Stevens experiences a bride's worst nightmare; being dumped at the altar. When she goes on the Caribbean cruise meant to be her honeymoon in order to lick her wounds, she discovers her ex-fiancé has sent his brother, Will Marshall, the former best man, on the cruise as well. Everyone on board thinks they're newlyweds, and Sarah is too embarrassed to set them straight. How is she supposed to share a tiny cabin with a man she barely knows? How is she supposed to pretend that she and Will are on their honeymoon? Even worse, how can she keep from falling in love with him? Sarah discovers the best man for her really is the best man.