Comic Title: Action Comics #379
Publisher: DC (National Periodical Publications, Inc.)
Address: 909 Third Avenue, New York, NY
Cover Date: August 1969
On Sale Date: June 26, 1969 Copyright Date June 26, 1969
Source: Library of Congress, Periodicals 1969


Newsstand Date June 26, 1969
Source: Comic Reader, #73

Frequency: Monthly (semi-monthly, March)
Cover Price: $0.15
Page Count: 32
Editor: Mort Weisinger

Title: "One of Us Is an Imposter"
Pages: 8

Feature(s):
Legion of Super-Heroes (of Earth-1)

Writer: E. Nelson Bridwell
Penciller: J. Winslow Mortimer
Inker: Murphy Anderson

Reprinted In:
Legion of Super-Heroes Archives Vol. 9 HC (2000)
Showcase Presents:Legion of Super-Heroes Vol. 4 TPB (2010)
Legion of Super-Heroes:The Silver Age Omnibus Vol. 3 HC (2020)

Feature Character(s)

• Legion of Super-Heroes (last appearance in Action Comics #378; next appearance in Action Comics #380)
• Lightning Lad (last appearance in Action Comics #378; next appearance in Action Comics #381)
• Mon-El (last appearance in Adventure Comics #380; next appearance in Action Comics #380)
• Element Lad (last appearance in Adventure Comics #376; next appearance in Action Comics #384)
• Dream Girl (last appearance in Adventure Comics #380; next appearance in Action Comics #384)
• Shadow Lass (last appearance in Adventure Comics #376; next appearance in Action Comics #384)

Villain(s)

• Sunburst (a sun powered villain; no further appearances)
• Uli Algor (disguised as Shadow Lass; real name not revealed in this story; first appearance; next appearance in Action Comics #386)

Synopsis:
The Legion computer alerts a small group of Legionnaires that one of them is an imposter. Before the computer can reveal the intruder's identity, it explodes. The Legion is then called away to battle Sunburst, a crook with solar powers similar to Sun Boy.

Dream Girl receives a vision that Sunburst will be defeated by his own power. Lightning Lad and Element Lad both fail to stop him and Mon-El is weakened when he attacks. Finally Shadow Lass is able to blind Sunburst, allowing Mon-El to knock him out.

After the battle the Legionnaires accuse each other of being the imposter. Only Shadow Lass's power seemed to work correctly. However, Mon-El unmasks her as the intruder. She was working with Sunburst in order to infiltrate the Legion.