In the opening prior to the scene in which your episode begins, Professor Rusk confronts Justin and Cooper with an accusation of having stolen a test. He also announces that Lieutenant Columbo will be the guest lecturer at an upcoming class. Getting back to the accusation, Rusk threatens to have Justin and Cooper either flunked or expelled from the college. They try to reason with him as he walks to his car. He does not bend at drives away. Justin and Cooper follow him in their own car.

They follow him to a restaurant, and the woman in the red dress is his lover June Clark, who is married to another man.

David - Thanks sir, everything now fits into place.

This episode is a particular favourite of ours, I was surprised just how late in the overall series it was released.

It's certainly one of the best later-Columbo's.