Wiseman, an inspector at an agency that reviews children's games and toys that are imported from other planets, comes across three play things from an alien race, known as the Ganymedeans. The first game, consisting of twelve soldiers and a citadel, offers simulated sieges of the citadel that the player is trying to defend. Wiseman; his colleague, Pinario; and their supervisor, Fowler, run iterations of the game to make sure that it is safe to use for children on their planet to play with. They notice after a week the citadel has absorbed one of the miniature soldiers — dismantling it piece by piece and absorbing it into the structure. While the war game runs, Wiseman and Pinario inspect another toy from the Ganymedeans that looks simply like an "American Cowboy Suit." Upon wearing it, Wiseman is transported into his younger self's mind on a ranch in the American West. He loses sight of his present reality and begins to think he is once again ten years old. Pinario pulls him out of the simulation and the two decide the game is unsafe to distribute. The citadel of the war game slowly absorbs more of the twelve soldiers. The third game, Syndrome (a board game similar to Monopoly), is played by Wiseman, Pinario, and Fowler. They believe it to be almost identical to Monopoly, and try to acquire stocks throughout the game. While they play, they talk about the war game and fear that it may be slowly assembling itself into an atomic bomb. They call in a bomb expert from the military who believes they should let the citadel absorb all of the soldiers before they make any judgement calls.  As they watch the war game absorb the last soldier, they do not shut it down in time and a reverberating message pours out from the citadel exclaiming their victory and promptly reassembles the soldiers — starting the game anew. The men decide that the game may be a red herring and decide to keep it for further inspection. They also withhold the American Cowboy Suit, but approve the Syndrome game. Joe Hauck, a manager of a children’s store, brings the unreleased Syndrome game home to his two children, by stealing a set from his warehouse. He plays it with his son and daughter, slowly acquiring more and more stocks until he believes he has them beat. His children inform him that according to the rules, the purpose of the game is to lose everything and the winner will have nothing at the end. Hauck is confused by this, having played Monopoly and knowing the purpose of that game, but accepts the new activity because of his children’s interest in it and the fact that it will be successful on the market.