Comic Title: Challengers of the Unknown #64
Publisher: DC (National Periodical Publications, Inc.)
Address: 575 Lexington Avenue, New York, NY
Cover Date: Oct/Nov 1968
On Sale Date: August 1, 1968 Copyright Date August 1, 1968
Source: Library of Congress, Periodicals 1968

Newsstand Date August 1, 1968
Source: Comic Reader, #68

Frequency: Bi-monthly
Cover Price: $0.12
Page Count: 32
Editor: Murray Boltinoff

Title: "Invitation to a Hanging"
Pages: 12

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

Writer: Robert Kanigher
Artist: Jack Sparling

Feature Character(s)

• Challengers of the Unknown (last appearance in Challengers of the Unknown #63; next appearance in Challengers of the Unknown #65)
• Ace Morgan (last appearance in Challengers of the Unknown #63; next appearance in Challengers of the Unknown #65)
• Red Ryan (last appearance in Challengers of the Unknown #63; next appearance in Challengers of the Unknown #65)
• Rocky Davis (last appearance in Challengers of the Unknown #63; next appearance in Challengers of the Unknown #65)
• Prof. Haley (last appearance in Challengers of the Unknown #63; next appearance in Challengers of the Unknown #65)

Villain(s)

• Doctor Hemlock (dies in this story; no further appearances)
• Wolf Dengon, Shark Powell, Snake Saunders, and their robot twins (all die in this story; no further appearances)

Other Character(s)

• Judge Bentley and John Evans (a district attorney; both die in this story; no further appearances)

Synopsis:
The Challengers are invited to the execution of three criminals who vow to seek revenge from the grave. After the convicts are killed, the judge and district attorney who convicted them are killed by their apparent ghosts. The Challengers investigate and discover the grave of their boss Doc Hemlock is empty.

The Challengers are captured and taken to Hemlock's hideout. The crook is actually still alive and is using robot duplicates of the executed convicts to exact his revenge. The Challengers escape captivity and destroy the robots. During the skirmish Hemlock becomes the fatal victim of his own noose.