Mary Anne Saves the Day is the fourth book in the original series.
Mary Anne Spier lives alone with her father who treats her like a baby. She is forced to wear her hair in braids, dress conservatively, and her bedroom looks like a nursery. After a client falls ill, Mary Anne's father is forced to see how responsible Mary Anne actually is.
This is the first appearance of Dawn Schafer, who will later join the club as an alternate officer.
The Baby-sitters Club get into a huge fight, and take turns holding meetings by themselves.