Comic Title: Superman #21
Publisher: DC (Superman, Inc.)
Address: 480 Lexington Avenue, New York, NY
Cover Date: Mar/Apr 1943
On Sale Date: December 30, 1942 Newsstand Date December 30, 1942
Source: House Ad, Action Comics #57, Page 16

Copyright Date January 2, 1943
Source: Library of Congress, Periodicals 1943
Until 1958 DC did not report actual on sale dates to the copyright office
The publication dates listed in LoC records are NOT release dates.

Frequency: Bi-monthly
Cover Price: $0.10
Page Count: 64
Editor: Jack Schiff

Title: (X-Alloy)
Pages: 13

Feature(s):
Superman (of Earth-2)

Writer: Jerry Siegel
Penciller: Joe Shuster
Inker: John Sikela

Reprinted In:
Superman Archives Vol. 6 HC (2003)
Superman:The Golden Age Omnibus Vol. 3 HC (2017)

Feature Character(s)

• Superman (last appearance in Action Comics #57; next appearance in Superman #21)

Supporting Character(s)

• Perry White (last appearance in Action Comics #57; next appearance in Superman #21)
• Sergeant Casey (last appearance in Superman #19; next appearance in Superman #21)

Villain(s)

• Frank Lingle (president of a steel company; no further appearances)
• Carlton Graul and a group of fifth columnists (no further appearances)

Comments:
This story originally was not titled; the title shown here was given on the contents page of Superman Archives Vol. 6 in which this story is reprinted.

Synopsis:
Clark Kent attends a demonstration of a new cannon built from an experimental X-Alloy. The cannon explodes killing the test personnel. Clark himself is kidnapped. When he confronts the kidnappers as Superman, they die from poison gas.

Superman investigates the steel factory where the X-Alloy was produced. He discovers that the factory is full of fifth columnists. The spies try to eliminate Clark, but Superman outwits them. Superman then forces the company president to confess that he is working with the spies because his son is held in enemy hands. Superman then stops a foreign missile attack, before delivering the story as Clark.