The Operation

While Brian and Sully are out hiking, Brian climbs a tree and jumps out before Sully can stop him. Brian lands hard, hitting his head. Mike, angry with Sully for not watching Brian more carefully, is relieved to find no signs of injury.
Later, the townsfolk argue over who will build the new schoolhouse, Matthew wants Robert E included, but, in the end Jake and Loren are tapped for the job. Brian begins to exhibit symptoms of compression, which escalate to blindness and later, coma. A specialist can't be found and Mike must perform a dangerous brain operation while Jake and Grace assist.
Meanwhile, the town, including Robert E, pulls together to build the schoolhouse. Brian awakens and wanders out to the new school where Mike and the family find him, overjoyed that he can see again.