Comic Title: World's Finest Comics #138
Publisher: DC (National Periodical Publications, Inc.)
Address: 575 Lexington Avenue, New York, NY
Cover Date: December 1963
On Sale Date: October 24, 1963 Newsstand Date October 22, 1963
Source: House Ad, Batman #160, Page 29

Copyright Date October 22, 1963
Source: Library of Congress, Periodicals 1963

Newsstand Date October 24, 1963
Source: Newsdealer Magazine, V18 #9

Frequency: Monthly, with the exception of Jan., April, July and Oct.
Cover Price: $0.12
Page Count: 32
Editor: Jack Schiff

Title: "The Secret of the Captive Cavemen"
Pages: 15

Feature(s):
Superman (of Earth-1)
Batman (of Earth-1)

Writer: Bill Finger
Artist: Jim Mooney

Reprinted In:
World's Finest Comics #206 (1971)
Showcase Presents:World's Finest Vol. 2 TPB (2008)
Batman & Superman in World's Finest Comics:The Silver Age Omnibus Vol. 2 HC (2019)

Feature Character(s)

• Superman (last appearance in Justice League of America #24; next appearance in Action Comics #307)
• Batman (last appearance in Justice League of America #24; next appearance in Detective Comics #322)

Supporting Character(s)

• Robin (last appearance in Batman #160; next appearance in Detective Comics #322)
• Carter Nichols (last appearance in World's Finest Comics #135; next appearance in Super Friends #10)

Villain(s)

• General Grote and a group of alien rebels (no further appearances)

Other Character(s)

• A tribe of cavemen (no further appearances)

Synopsis:
Batman and Robin encounter a group of aliens who claim that the Earth is doomed, then disappear into the past. Using Professor Nichols’s time machine Batman, Robin, and Superman travel to the days of prehistoric cavemen to learn the alien secret.

They discover that the aliens are capturing cavemen using mind-controlling z-beams. The heroes allow themselves to be captured, though the z-beams have no effect on their modern minds. They are put to work as slaves on an alien world mining raw drakkium. Superman loses his powers, due to the planet’s red sun, but the heroes still manage to defeat the alien plot, turning them over to the authorities and saving Earth from an invasion.