Contents (view Concise Listing)

• ix • Introduction (Invaders of Earth) • (1952) • essay by Groff Conklin
• 1 • Prologue: The Distant Past • (1952) • essay by uncredited
• 2 • This Star Shall Be Free • (1949) • novelette by Murray Leinster
• 23 • Part One: The Immediate Past: It Could Have Happened Already • (1952) • essay by uncredited
• 24 • Impulse • (1938) • short story by Eric Frank Russell
• 37 • Top Secret • (1948) • short story by Donald A. Wollheim [as by David Grinnell]
• 40 • An Eel by the Tail • (1955) • short story by Allen Kim Lang [as by Allan Lang]
• 52 • Storm Warning • (1942) • short story by Donald A. Wollheim [as by Donald Wollheim]
• 64 • Tiny and the Monster • (1947) • novelette by Theodore Sturgeon
• 102 • The Discord Makers • (1950) • short story by Mack Reynolds
• 115 • Pen Pal • (1951) • short story by Milton Lesser
• 131 • Part Two: The Immediate Future: It May Happen Yet • (1952) • essay by uncredited
• 132 • Invasion from Mars • (1938) • novelette by Howard Koch (variant of The Invasion from Mars: A Radio Adaptation)
• 158 • Minister Without Portfolio • (1952) • short story by Mildred Clingerman
• 167 • Crisis • (1951) • short story by Edward Grendon
• 178 • Angel's Egg • (1951) • novelette by Edgar Pangborn
• 219 • "Will You Walk a Little Faster?" • (1951) • short story by William Tenn (variant of "Will You Walk a Little Faster")
• 232 • Pictures Don't Lie • (1951) • short story by Katherine MacLean
• 253 • Epilogue: The Distant Future • (1952) • essay by uncredited
• 254 • The Greatest Tertian • (1952) • short story by Anthony Boucher