Comic Title: Adventure Comics #394
Publisher: DC (National Periodical Publications, Inc.)
Address: 909 Third Avenue, New York, NY
Cover Date: June 1970
On Sale Date: April 30, 1970 Copyright Date April 30, 1970
Source: Library of Congress, Periodicals 1970

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

Title: "Heartbreak Prison"
Pages: 13

Feature(s):
Supergirl (of Earth-1)

Writer: Robert Kanigher
Artist: Kurt Schaffenberger

Feature Character(s)

• Supergirl (last appearance in Adventure Comics #394; next appearance in Superman #229)

Villain(s)

• Tyrox (an interplanetary tyrant; no further appearances)
• Robot and humanoid guards employed by Tyrox (no further appearances)

Other Character(s)

• Yo-La, Tyy-Ra, and several other heroines (no further appearances)

Synopsis:
Supergirl receives a distress call which originates from outer space. The message warns of a zenith weapon that must be destroyed. By following the distress call, Supergirl travels to a world ruled by the tyrant Tyrox. She allows herself to be captured in order to find the secret weapon.

Supergirl is imprisoned in a colored cell alongside other female prisoners. Tyrox and his guards treat the prisoners with cruelty. Supergirl must refrain from using her powers because the other prisoners will be punished for her actions.

Eventually Supergirl discovers the secret of the zenith weapon and begins to oppose her jailor. However, Tyrox uses Kryptonite to weaken her, then turns the planet's sun red to rob Supergirl of her powers. However, the other female prisoner use the opportunity to escape. Each is a heroine from other planets who have also responded to the distress call. They take down Tyrox and free Supergirl. With the threat ended, Supergirl returns to Earth.