Leper is with the boys when they jump from the tree the first time; he declines to join them.
When Leper does finally decide to do a jump, Gene and Phineas come with him to the tree. They climb first to do their double jump, which is when Finny falls and breaks his leg.
When the normal school year starts in September, Leper and his collection of snails have moved to a different dorm.
When Gene heads off to help clear snow from the railroad tracks, he bumps into Leper, who is cross-country skiing and looking for a beaver dam.
When he boys come back from clearing the railroad tracks, Brinker makes fun of Leper for being a naturalist.
In awe of the ski troops he sees on a recruiting video, Leper joins the army.
Back at Devon, the boys imagine Leper's participation in all the biggest war goings-on.
Leper sends a telegram to Gene saying that he's escaped, is hiding out at "Christmas location," and needs help at once. He signs it "Your best friend."
Gene discovers that Leper has gone mad. It's also clear that Leper believes Gene responsible for Finny's accident. He describes a variety of his psychotic visions, all having to do with odd transformations.
Leper comes back to Devon and is seen hiding in the shrubbery about campus.
He is called as a witness during Brinker's assembly hall "investigation." He gives the truth in a round-about way and finally stops himself, calling Brinker a bastard and refusing to answer any more questions.