Contents (view Concise Listing)

• 9 • Introduction (Invaders of Earth) • (1952) • essay by Groff Conklin
• 15 • Prologue: The Distant Past • (1952) • essay by uncredited
• 16 • This Star Shall Be Free • (1949) • novelette by Murray Leinster
• 41 • Part One: The Immediate Past: It Could Have Happened Already • (1952) • essay by uncredited
• 42 • Castaway • (1941) • short story by Robert Moore Williams
• 61 • Impulse • (1938) • short story by Eric Frank Russell
• 76 • Top Secret • (1948) • short story by Donald A. Wollheim [as by David Grinnell]
• 79 • A Date to Remember • (1949) • short story by William F. Temple
• 97 • Child of Void • (1949) • short story by Margaret St. Clair
• 116 • Tiny and the Monster • (1947) • novelette by Theodore Sturgeon
• 161 • The Discord Makers • (1950) • short story by Mack Reynolds
• 176 • Not Only Dead Men • (1942) • short story by A. E. van Vogt
• 205 • Part Two: The Immediate Future: It May Happen Yet • (1952) • essay by uncredited
• 207 • Invasion from Mars • (1938) • novelette by Howard Koch (variant of The Invasion from Mars: A Radio Adaptation)
• 236 • Minister Without Portfolio • (1952) • short story by Mildred Clingerman
• 246 • The Waveries • (1945) • short story by Fredric Brown
• 276 • Crisis • (1951) • short story by Edward Grendon
• 289 • Angel's Egg • (1951) • novelette by Edgar Pangborn
• 338 • "Will You Walk a Little Faster?" • (1951) • short story by William Tenn (variant of "Will You Walk a Little Faster")
• 353 • Pictures Don't Lie • (1951) • short story by Katherine MacLean
• 377 • Epilogue: The Distant Future • (1952) • essay by uncredited
• 378 • The Greatest Tertian • (1952) • short story by Anthony Boucher