Gary Elringer invites a group of family members and friends, all stockholders in a corporation he started, to spend a weekend at the computer-operated house into which he has been investing the company’s funds. Elringer, an extremely disagreeable yet charismatic computer genius, believes that he will be able to convince his business partners that the fully automated house is the next technological step in home living. In order to make his guest “use” Smart House, Elringer has arranged that everyone play a game of Assassin. The computer assigns each player a victim, oversees the choice of weapons, and keeps track of the “kills” and new victim assignments. When Elringer and another stockholder are found actually dead and the house is the most likely suspect, the stockholders decide to hire Constance and Charlie to find the real murderer in order to clear the house of suspicion and avoid scandal.
Upon their arrival at Smart House, Charlie and Constance are introduced to a group of unhappy shareholders, none of whom enjoys the others’ company and all of whom have a motive for killing Elringer. The detectives use their extraordinary intelligence and intuition to unravel the bizarre twists in this case. Wilhelm makes plausible the strong psychic affinity between Constance and Charlie, which enables them to work together effectively. A third murder and their own close escape from a horrible death increases their determination to solve the case.