It's official! Mary Anne’s father and Dawn’s mother are getting married! The Baby-sitters think it’s so romantic, especially since Mr. Spier and Mrs. Schafer first fell in love when they were in high school. But nothing can top Mary Anne and Dawn’s excitement. They want a huge wedding with beautiful dresses, lots of presents and a five-layer cake. After all, this isn’t just any wedding. Mary Anne and Dawn are going to be baby-sitters, best friends and sisters, too!