Harold Van Wick is in charge of Meadis Electronics, a company owned by his mother-in-law Margaret Meadis. However, Harold has a fascination with inventing electronic gadgets and is channelling the company's funds into unprofitable side-projects. Margaret demands Harold's resignation and threatens him with revealing his romantic affairs, which she has discovered using a private detective, if he refuses.
Harold decides to eliminate Margaret, and plans to use the electronic surveillance system he has installed in his home to provide him with the perfect alibi. First, he sets the scene by making it look like a burglar has broken in through a side-window. Then, he substitutes a video of an empty room in place of the live camera feed so that the security guard thinks nothing is happening. During this time, Harold, hidden in the shadows, shoots Margaret as she comes to investigate the noise of the "burglar" breaking in.
However, Harold records the shooting on another video tape, and then sets up a timer so that the security guard sees the killing later, when Harold is attending a reception at an art gallery.
Despite pretending to be overwhelmed by the technology, Columbo discovers a way of using Harold's own gadgets against him.
Although the 1970s technology looks dated now (there is even a "gosh, look at that!" moment when Columbo sees Harold's digital watch), the device of using swapped video tapes to cover up crimes and provide alibis has been used many times since, so this episode was a bit of a trend-setter for later detective shows.