A key element in A Separate Peace, the setting of Devon School has been the site of the private wars of Gene Forrester.  As an adult, he returns to this location in order to reach a resolution to the conflicts of his youth:

So it was logical to hope that since the buildings and the Deans and the curriculum could achieve this [harmony], I could achieve, perhaps unknowingly already had achieved, this growth and harmony myself.

THE RIVER AND THE TREE

This setting is the pivotal scene as it is here that a relationship between Gene and Phineas is established.  In Chapter 2 when Finny makes Gene jump first, Gene nearly falls, but Finny reaches back and saves him.  However, in Chapter 5, mistakenly attributing a deadly rivalry between him and Finny, Gene jounces the limb and allows Finny to fall. This scene in Chapter 5 is crucial to the irrational anger that has ruined Gene's friendship with Finny and his own self-understanding.  And, Gene as an adult revisits this crucial scene in order to arrive at self-realization.

THE BEACH

At the end of Chapter 3, as they walk back to the dorm, Finny suggests that they go to the beach, a forbidden area.  At this location, "pure as the shores of Eden," the suggestion of a Cain/Abel motif is introduced as Gene states,

...I detected that Finny's was a den of lonely, selfish ambition.

But, he later realizes,

He had never been jealous of me for a second. Now I knew that there never was and never could have been any rivalry between us.  I was not of the same quality as he.

With this Eden-like motif, Gene's fall into the Naguamsett river that he must wash off the sticky salt in Chapter 7 is seen, in contrast to the beach, as a reverse-baptism which effects many of Gene's further actions.

THE BUTT ROOM

Here a mock-trial takes place as Brinker accuses Gene of purposefully jouncing the tree limb.

THE WINTER CARNIVAL

In the scene of the Winter Carnival, in his separate world of sport, Finny creates a peace for him and Gene, "a libertion ...torn from the gray encrachments of 1943."  Here the descriptions of setting change as the carnival contrasts greatly with the stone gray of the war, and the carnival is held next to the sullied Naguamsett River.  Here, too, Gene remains a part of Finny, unable to stand apart on his own.

LEPER'S HOUSE

At Leper's house, where the AWOL soldier is, Gene interprets Leper's actions as selfish, failing to recognize his own actions as such.  For, since Leper's narration of the war discomforts Gene who wishes to remain in the peace of Devon, he pushes Leper out of his chair.

THE ASSEMBLY ROOM

In Chapter 11, Brinker furthers his prosecution of Gene, suggesting to him that maybe Finny did not "just fall out of that tree." At this trial, Finny runs from the truth and falls down the marble steps.

THE INFIRMARY

When Gene visits Finny, for the first time Finny admits to the "terrible mess" of the war.

WORLD WAR II

In Chapter 3 Gene remarks,

Everyone has a moment in history which belongs particularly to him [as] his emotions achieve their most powerful sway over him...when you say to this person "the world today" or "life" or "reality" he will assume you mean this moment, even if it is fifty years past.  The world, through his unleashed emotions, imprinted itself upon him, and he carries the stamp of that passing moment forever.

With the backdrop of WWII, Gene concludes that he has been "on active duty all the time" at Devon. For, his private evil parallels the evil of the war.