Gerry is turning forty, and after finding a letter he wrote to himself ten years earlier, he becomes acutely aware of everything he has failed to accomplish. Meanwhile, Simon's ferret goes missing and Lisa wants to impress the chairman of the board of trustees by putting on an elaborate fun fair in his honour, which quickly devolves into a complete disaster.
Based on Gerry Dee's real-life experiences as a high school teacher before he switched to comedy full-time, MR. D is a story about a charming, under-qualified teacher trying to fake his way through a teaching job, just like he often fakes his way through life. The premise shines the light on teaching from the teacher's point of view, and as it turns out, teachers don't know everything, especially Mr. D - who struggles to keep one step ahead of his students.