A nervous and worried father asks Astro Boy, Dr. Elefun, and Mr. Pompous to come at once to his western ranch. There he confides to them that his son, Heck, has disappeared. The young man, always in love with the romantic Old West, built a time machine, vanished into the past, and never returned. Astro Boy and his friends agree to help the anxious father. Using the same time machine, they go back to the Old West. They find Heck, only to discover that he is apparently mixed up with a gang of no-good, shiftless varmints; bank robbers and such. To make matters worse, the local townspeople suspect Astro Boy and his dude friends of having committed the bank robbery that took place the day of their arrival. The three strangers are strung up under a tree and face a lynching. Things look bad. Suddenly, Astro Boy hits upon a plan: he convinces the townsfolk to give him 24 hours to bring the real crooks in. So begins a whirlwind roundup. The real crooks are brought to justice, but not before Mr. Pompous is forced into an old-fashioned gunfight and Astro Boy has to do some fancy shooting!