Comic Title: Action Comics #406
Publisher: DC (National Periodical Publications, Inc.)
Address: 909 Third Avenue, New York, NY
Cover Date: November 1971
On Sale Date: September 30, 1971 Newsstand Date September 30, 1971
Source: House Ad, Adventure Comics #412, Page 47

Copyright Date September 30, 1971
Source: Library of Congress, Periodicals 1971

Frequency: Monthly
Cover Price: $0.25
Page Count: 48
Editor: Murray Boltinoff

Title: "The Challenge of the Expanding World"
Pages: 13

Feature(s):
Atom (Ray Palmer of Earth-1)
Flash (Barry Allen of Earth-1)

Writer: Bob Haney
Artist: Alexander Toth

Reprinted From:
Brave and the Bold #53 (1964)

Feature Character(s)

• Atom (last appearance in Atom #12; next appearance in Justice League of America #27)
• Flash (last appearance in Justice League of America #26; next appearance in Flash #144)

Supporting Character(s)

• Iris West (last appearance in Flash #143; next appearance in Flash #144)

Villain(s)

• Attila-5 and his followers (no further appearances)

Other Character(s)

• Dr. Willis Stanton (a scientist; no further appearances)
• Larnus and Arbellice (a scientist from the green world and his daughter; no further appearances)

Synopsis:
Central City is menaced by several strange alien threats. Flash handles each emergencies, then tracks the source of the trouble to the lab of Dr. Willis Stanton. Stanton has contacted the Atom to help experiment with a strange green sphere from space. When Flash arrives, he uses his super speed to throw Atom into the sphere replacing a missing electron.

Once inside the sphere, Atom finds a sub-atomic world. He accidentally prevents Larnus, a scientist of that world from being captured. Larnus explains that the world's tyrant ruler Attila-5 has controlled Stanton, and because of Atom's actions, the green sphere is expanding, and will endanger the Earth.

Outside the sphere Flash is kayoed by Stanton. When he revives, he tracks the sphere to Hadleyville where it has begun to grow. Flash vibrates at super speed to enter the sphere, where he suddenly loses his powers. Attila-5's aircraft then take him down.

Atom defeats Attila's fleet, then rescues the Flash. As the sphere has grown larger, Flash's powers have returned. The two heroes exit the sphere and use a device given to the by Larnus to stop the sphere's expansion. The device divides the spheres, then Atom and Flash force the spheres together causing them to explode. A smaller sphere containing the sub-atomic world survives the explosion. Larnus and the scientists gain control from Attila-5, then take the world into space where they can expand it without danger to Earth.