Corneil is an intelligent dog: not only can he read and write perfect English, but he is much smarter than most people. Since he is so smart, he knows that life does not get any better than being a pampered pet, and so he does anything he can to keep his owners John and Beth from realizing his phenomenal skills.
This plan begins to go awry when they hire the pinheaded Bernie Barges to “dog-sit”, and Bernie learns about Corneil’s secret.