Comic Title: Challengers of the Unknown #69
Publisher: DC (National Periodical Publications, Inc.)
Address: 909 Third Avenue, New York, NY
Cover Date: Aug/Sep 1969
On Sale Date: June 3, 1969 Copyright Date June 3, 1969
Source: Library of Congress, Periodicals 1969

Newsstand Date June 3, 1969
Source: Comic Reader, #73

Frequency: Bi-monthly
Cover Price: $0.15
Page Count: 32
Editor: Murray Boltinoff

Title: "The Secret of Skull Mountain"
Pages: 23

Feature(s):
Challengers of the Unknown (of Earth-1)

Writer: Dennis J. O'Neil
Artist: Jack Sparling

Feature Character(s)

• Challengers of the Unknown (last appearance in Challengers of the Unknown #68; next appearance in Challengers of the Unknown #70)
• Ace Morgan (last appearance in Challengers of the Unknown #68; next appearance in Challengers of the Unknown #70)
• Red Ryan (last appearance in Challengers of the Unknown #68; next appearance in Challengers of the Unknown #70)
• Rocky Davis (last appearance in Challengers of the Unknown #68; next appearance in Challengers of the Unknown #70)
• Prof. Haley (last appearance in Challengers of the Unknown #68; next appearance in Challengers of the Unknown #70)

Supporting Character(s)

• Corinna Stark (next appearance in Challengers of the Unknown #70)

Villain(s)

• Eli Swade (a biologist; no further appearances)
• Algernon Stark (Corinna Stark's father; next appearance in Challengers of the Unknown #70)

Other Character(s)

• An unnamed murder victim (no further appearances)

Comments:
This story continues in part in Challengers of the Unknown #70.

Synopsis:
The Challengers are called to Stark Mountain to investigate a murder in which the suspect is a dead man. They encounter a hulking man who easily defeats them, then he disappears into the forest. The Challs follom him to a castle owned by Algernon Stark.

The team enters the castle and discovers evidence that the giant man is inside. Stark allows them to search the castle. Prof is then taken over by evil impulses and attempts to kill Rocky. He fails and the other Challs realize that their friend has secretly been trying to kill each of them.

The Challs then hear the scream of Corinna Stark who is threatened by the giant man who resembles the dead biologist Eli Swade. Corinna explains that the monster is a robot that her father was using in hopes of unlocking the secrets of immortality with Swade. Prof sacrifices himself to save the team, but he is shot. Corinna places his body into cryogenic storage then offers to join the Challengers as Prof's replacement.