It's Valentine's Day and the class is selling lightbulbs. When they stop at Ms. Frizzle's house to sell her one, they find that her battery-operated doorbell doesn't work. While looking for Ms. Frizzle to tell her the doorbell's broken, Wanda overhea... (more)rs her teacher talking on the telephone. ""Ms. Frizzle has a boyfriend,"" says Wanda, ""and he's on his way over to see her! We've got to fix the doorbell or she'll never know he's here!"" But first they have to figure out how the doorbell works...