One stormy summer night, a cow named Thorn is ready to have a new calf. The farmer and his wife are very nervous. What if the cow gives birth during the thunderstorm?

Late that night, unable to sleep, they grab their raincoats, an umbrella, and a flashlight and head out to the field to see if Thorn is okay. Once they make it out to the dark and rainy field, they get a very big surprise. Thorn has had not one but two calves—one with a white slash on its forehead and the other with a fluffy white patch. Then and there, they decide to call the calves Thunder and Lightning. But what sort of mischief will these twin calves find as they grow up?

This children's story tells the tale of the birth of twin calves named Thunder and Lightning on a dark and stormy summer night.