How does Mom and Dad's argument escalate?

In Part II. Rex and Rose Mary get into an argument over the duration of her pregnancy with their first child. Rex has been drinking, Rose Mary doesn't like his hostility, and as a result.... she jumps out of the moving car. Subsequently, Rex follows her with the car, leading the children to fear he's going to hit her. When he finally corner her, he gets out and throws her back into the car.