Arnold wants to know what happened to the heat from his hot cocoa. Ms. Frizzle thinks it is fitting to learn about heat in the land of ice and cold, so she takes the class to the Arctic. However, she accidentally drives the bus into the water, and the bus freezes. To make matters worse, the bus has been trapped on an ice floe with Phoebe, Ralphie and Liz. The class will have to get to the bus and heat it up to escape.