Summary of 'The Book That Saved the Earth'

The play begins on Mars, where the Martian Commander-in-Chief, Think-Tank, is planning to invade Earth. He has a massive, balloon-like head and considers himself the most intelligent creature in the universe. He orders his crew (Captain Omega, Lieutenant Iota, and Sergeant Oop) to land on Earth and gather intelligence.

The crew lands in the Centerville Public Library on Earth. Having never seen books before, they have no idea what they are. Think-Tank, communicating from Mars, guesses that the books are 'sandwiches' (the staple diet of Earthlings) and even forces Sergeant Oop to eat a corner of a book! Later, he decides they are communication devices.

To read the books, the crew swallows 'vitamin pills' to boost their intelligence. They randomly open a book of children's nursery rhymes called Mother Goose. When they read poems like 'Humpty Dumpty' and 'Hey Diddle Diddle', Think-Tank takes the silly rhymes completely literally.

When Think-Tank hears the rhyme 'The cow jumped over the moon', he assumes Earthlings are so scientifically advanced that even their animals can travel in space. Finally, when he sees a picture of 'Humpty Dumpty', he thinks the Earthlings have drawn a picture of his own large head, and the rhyme 'had a great fall' means the Earthlings are plotting to overthrow him. Terrified, Think-Tank cancels the invasion immediately and orders his entire army to evacuate to the distant star Alpha Centauri.