Mercury or Venus.life or death? Such was the riddle posed to the four pioneers who first voyaged to those worlds. For on one planet they found the "harsh" virtues raised to the ultimate degree, and on the other the so-called "gentle" virtues glorified. What they decided coudl chart the way for all humanity! Here is a classic interplanetary adventure of strange civilizations and strange planets, as written by the brilliant co-author of THE BLIND SPOT.