Freddy reads an article announcing that Mr. Garble encountered a flying saucer and that Martians are displayed at Mr. Boomschmidt's circus.

Garble allows limited viewing of the Martians, so he must be lured away while Freddy's cohort Mrs. Peppercorn sneaks in.

She finds the bearded Martians dressed in red costumes with gloves, and oddly "like a dog walking on its hind legs".

Later, Freddy is successful investigating: in getting the "Martians" to agree that Mars is nearer the sun than the Earth, he realizes they must be fakes.

In confirming that the revolving chicken house door cannot be entered by the large snake, he is stuck, squeals loudly, and rouses the barnyard.

Rats being difficult to dislodge, Freddy makes use of ten sacks of rotten onions to taint the food at the Garble place.

Freddy lives on the Bean farm with animal friends: a cat, dogs, cows, chickens and rabbits, as well as a great variety of birds and insects: several play a role in this book.

Simon is a vicious, deceitful rat who heads a family gang, often plotting revenge on Freddy.

There are 42 black and white, pen and ink drawings by Kurt Wiese, endpapers, a frontispiece and a full color cover depicting scenes from the book.

'Freddy and the Men from Mars' is a case in point....Excitingly and amusingly, with the entry of real Martians, all is resolved."

It is noted that Brooks took a political risk during the McCarthy era, making fun of those who labeled others as communists on flimsy evidence.