After years of looking for Mr. Right, Charlotte "Charlie" Cantilini (Jennifer Lopez) finally finds the man of her dreams, Kevin Fields (Michael Vartan), only to discover that his mother, Viola (Jane Fonda), is the woman of her nightmares. A recently fired national news personality who is afraid she will lose her son the way she has just lost her career, Viola determines to scare off her son's new fiancée by becoming the world's worst "Monster-In-Law." While Viola's long time assistant, Ruby (Wanda Sykes), does her best to help Viola execute her crazy schemes, Charlie decides to fight back, and the gloves come off as the two women battle it out to the finish.