Because it was sandwiched between the exceptional comedies Grandma's Boy and Safety Last, Doctor Jack is one of Harold Lloyd's lesser-known features. Nevertheless, it's quite charming and actually did even better at the box office than Grandma's Boy, which was Lloyd's first true feature. Doctor Jack (Lloyd) is a nice young country doctor who prefers to use common sense and his sunny personality to effect cures instead of resorting to pills and potions. His most challenging case comes when a rich father (John T. Prince) asks him to look after his daughter (Mildred Davis, who, a few months after this film's release, would become Mrs. Harold Lloyd). The girl is being cared for by Dr. Ludwig von Saulsburg (Eric Mayne), who claims to be an eminent specialist. He keeps her in a darkened room and has prescribed her various medications. It takes Dr. Jack only a moment to figure out there is nothing wrong with the girl that a little sunshine and excitement won't cure. Von Saulsburg, who has been making a comfortable living off of the girl's family, is horrified by the country doctor's approach; to make matters worse, the girl falls in love with Dr. Jack. Their romance gets Dr. Jack thrown out of the house, but he gets back in the family's good graces by a little trick: Disguised as a lunatic, he terrorizes the household, then dressed as himself, he comes to the rescue. Along the way he makes a fool of the eminent Dr. Von Saulsburg. The excitement proves that the girl is perfectly healthy -- and ready to become Dr. Jack's wife.