Simon Kress, a wealthy playboy on the planet Baldur, loves to collect dangerous, exotic animals. One day, he stumbles across a mysterious establishment called Wo & Shade, where he purchases a terrarium filled with four colonies of creatures called sandkings, which grow to fill whatever environment they are kept in. Each colony consists of a large female called the maw, and numerous insect-like mobiles. In addition to finding food for the maw, the mobiles protect her from invading colonies. Indeed, the four colonies often engage in coordinated wars with one another, especially once their new owner makes them fight over food by starving them. Simon begins taking bets on the outcomes of these wars, which leave some of his friends impressed, and others disgusted. Eventually, the sandkings escape Simon's terrarium and begin to take over his house as their hunger—and Simon's desperation—intensifies.