Accompanied by MacDuff, Dirk returns to St Cedd's Institute of Science and Technology, Cambridge, from which he had been expelled for cheating, as his former mentor Professor Jericho has asked for his help in guarding Elaine, a sophisticated robot named after his daughter, used in his research into artificial intelligence. When Elaine is stolen, Dirk investigates seeing Jericho's colleague Emelda as the prime suspect. MacDuff meanwhile is tempted to leave Dirk's agency as his girlfriend, Susan, has applied for a job in Cambridge.

Dirk is in the frame when two of his former clients are killed and plans to skip the country though he is waylaid when Melinda Fulstone asks him to identify her stalker - actually Dirk himself conducting an experiment. Dirk believes the murderer is Robbie Glover, whom he accidentally had convicted for killing his own brother - particularly when Robbie tries to strangle him. But soon Dirk works out that Robbie has been framed and that there is somebody nearer home with a grievance against him.