chunk: Two weeks before the Ares is scheduled to leave Mars, Captain Harrison sends American chemist Dick Jarvis and French biologist "Frenchy" Leroy to retrieve the film Jarvis took before his auxiliary rocket crashed into the Thyle highlands the week before. Along the way, the Earthmen stop at the city of the cart creatures and the site of the pyramid building creature for Leroy to take some samples. After picking up the film canisters from the crashed rocket at Thyle II, the two men fly east to Thyle I to look for signs of the birdlike Martian, Tweel.
  Near a canal, the men find a strange, deserted city thousands of years old. The buildings are inhabited by birdlike Martians of Tweel's species, including Tweel himself, and Jarvis and the Martian enjoy a happy reunion. Jarvis persuades Tweel to guide them through the city.