Notice the scene where Mary is crying hysterically as she admits to Charles that Jasper bit Laura. The camera is zoomed in closely on Mary's face. Back when it was filmed, they planned on adding shots of Charles' face later, but Michael Landon became very ill with meningitis and was hospitalized. The episode was left incomplete, and Landon was not well enough to film anything else for it, so they just kept the close-up shots of Mary. Melissa Sue Anderson, the actress who played her, has said that this was one of her first really "meaty" roles on the show, and it gave her a chance to show that she could act.