Mr. De Vil is introduced in the Dodie Smith novel as Cruella's husband. When Mrs. Dearly questions what her marriage name is, Cruella states that since she is the only De Vil, she had her husband change his surname to hers. Her main reason for marrying him is for his occupation, a furier in which he is able to make her fur coats.
Mr. De Vil is shown to suffer a bit due to Cruella, such as having to make extremely hot fires and eating food which tastes like pepper. When the Dearlys hold a dinner party and invite the De Vils, Mr. De Vil is shown to eat much more of the non-peppered foods than he did of the food he has at his home.
When the white Persian tells the Dalmatians of Cruella fleeing to France, they comment pity on Mr. De Vil. The Persian assures them, though, that he is just as bad as Cruella, but is weak and bad (whilst Cruella is strong and bad).
When investigating during The Starlight Barking, the Dalmatians discover Cruella and her husband in France making metal raincoats.
Mr. De Vil is given the name of Harry in the musical. When he tries to explain to his guests about the night of when he met Cruella, Cruella butts in, telling him to get on with it, and he skips to, "It's been that way, ever since..." before introducing Cruella to her song, "Hot Like Me".