When someone slips a mean valentine that appears to come from George into Bess's pocket while the girls are making stuffed animals, Nancy's best friends are soon in the middle of a fight.
Nancy's good friend, Charlie, appears to be guilty of snake-napping from the River Heights Zoo. Meanwhile, George's brother, Scott, is being very sneaky and not acting like himself. Can these things be related? Nancy is about to find out.
When the class float is sabotaged before the Earth Day parade, it is up to eight-year-old Nancy Drew and the members of her detective club to find out who did it.