Dr. Marshal Cahill, head of a think tank, is forced to protect his plagarizing son by killing the professor, Nichols, who discovered the plagarized information. Cahill programs a robot to take his place during a war game exercise that he runs from an isolated room, then fakes a hit-and-run accident on Nichols and plants evidence to make it look like a drug theft gone awry. The first thing Columbo notices upon arrival is a match burned down to the base - something Columbo knows well because it's how you light a cigar. And Dr. Cahill is the only other cigar smoker around. There are a lot of other little things that Columbo notices as well, and with the help of a child prodigy he discovers how Cahill used the robot to provide himself with an alibi. But without one major clue, Columbo arrests the son to force Cahill, who was willing to kill for his son, to confess his crime to protect the boy.