Cassal stretched his stride and managed to keep the man in sight. He skipped nimbly over the narrow walkways that curved through the great buildings. The section grew dingier as they proceeded. Not slums; not the show-place city frequented by travelers, either. Abruptly the man turned into a building. He was out of sight when Cassal reached the structure. He stood at the entrance and stared in disappointment. "Opportunities Inc.," Dimanche quoted softly in his ear. "Science, thrills, chance. What does that mean?" "It means that we followed a gravity ghost!" "What's a gravity ghost?" "An unexplained phenomena," said Cassal nastily. "It affects the instruments of spaceships, giving the illusion of a massive dark body that isn't there." "But you're not a pilot. I don't understand." "You're not a very good pilot yourself. We followed the man to a gambling joint." "Gambling," mused Dimanche. "Well, isn't it an opportunity of a sort? Someone inside is thinking of the money he's winning." "The owner, no doubt." Dimanche was silent, investigating. "It is the owner," he confirmed finally. "Why not go in, anyway. It's raining. And they serve drinks." Left unstated was the admission that Dimanche was curious, as usual. * * * * * Cassal went in and ordered a drink. It was a variable place, depending on the spectator--bright, cheerful, and harmonious if he were winning, garish and depressingly vulgar if he were not. At the moment Cassal belonged to neither group. He reserved judgment. An assortment of gaming devices were in operation. One in particular seemed interesting. It involved the counting of electrons passing through an aperture, based on probability. "Not that," whispered Dimanche. "It's rigged." "But it's not necessary," Cassal murmured. "Pure chance alone is good enough." "They don't take chances, pure or adulterated. Look around. How many Godolphians do you see?" Cassal looked. Natives were not even there as servants. Strictly a clip joint, working travelers. Unconsciously, he nodded. "That does it. It's not the kind of opportunity I had in mind." "Don't be hasty," objected Dimanche. "Certain devices I can't control. There may be others in which my knowledge will help you. Stroll around and sample some games." Cassal equipped himself with a supply of coins and sauntered through the establishment, disbursing them so as to give himself the widest possible acquaintance with the layout. "That one," instructed Dimanche. It received a coin. In return, it rewarded him with a large shower of change. The money spilled to the floor with a satisfying clatter. An audience gathered rapidly, ostensibly to help him pick up the coins. "There was a circuit in it," explained Dimanche. "I gave it a shot of electrons and it paid out." "Let's try it again," suggested Cassal. "Let's not," Dimanche said regretfully. "Look at the man on your right."