A sort of a tip of the hat to the play "Wait Until Dark", this episode has the backdrop of the dark and nearly deserted blind school to make your nerves tingle as Mary and Laura are taken upon by 3 criminals on a stormy night.
One of the men is badly wounded and sends Laura out to find a doctor. Although this seems an unlikely scenerio, it works here. After all, Laura is assured of harm coming to her blind sister if she alerts authorities. Unable to find Dr. Baker, she goes to Pa, who decides he must take things into his own hands. Posing as Dr. Baker (how quickly Mary catches on!), he sets the stage for the bad guys' undoing.
Several wrong turns later,the real Baker shows up,revealing Pa's ruse. Baker is knocked out and Mary, in the hands of an attacker, is able to get away. In the darkness of the school, the man tries to find her while Pa stalks him. Here are the most tense moments of the episode. After orienting himself, and being frightened by a cat, the bad guy finally corners Mary. When all is about to be lost, Pa, thought to be seriously injured, finally crashes the bad guy over the head and saves the day. I don't feel, as some do, that this is contrived at all. We know that Charles has is the past overcome insurmountable obstacles to preserve his own and he doesn't disappoint here. The momentary panic of his discovered identity and Mary's evasion of the bad guy provide edge of the seat tension that is richly rewarded when all is resolved. A fine and suspensful episode.