The plot structure is a narrative told from the future about the past. This means that the events in the narrative, occupying the "present" moment, are a reminiscence told by the narrator as a grown woman, from some future time in her life, about events that happened in her past when she was fifteen. The plot can be described in terms of Freytag's pyramid plot structure, with exposition, rising action, climax, falling action and resolution. Occurrences follow a generally chronological progression, but flashback is used to give background:

I was fifteen and away from home for the first time. My parents had made the effort and sent me to high school for a year, but I didn't like it. ... Dr. Peebles' ... wife was looking for a girl to help. ... [W]orking there ... [I] was feeling half hungry all the time. I used to bring ... a box of doughnuts ... but I thought I better bind [the children] to secrecy.

The flashback helps initiate the rising action, which commences after the flashback: "the day after the plane landed...." Suspense and tension are heightened when Edie finds Mrs. Peebles' dress, "a satin [dress], a lovely weight on [her] arm." A complication in the rising action occurs when she sees a man through the screen door, Chris Watters, the pilot of the plane. More rising action occurs with a twist added when "Alice Kelling, Mr. Watters' fiancee" is introduced. And complications occur when Edie and Watters are alone together, he finally needing to splash cold water to "cool us off."

The climax comes after Watters flies off and Alice, in a rage that he's gone and that Edie didn't say right away that he was, accuses Edie of being a "tramp" and of having "intimate" relations with Watters. Edie, not knowing the deeper meaning behind the accusation of an act of intimacy, confesses that she was, in fact, intimate with him. Only after an appalling and loud discussion of horrific pregnancies of "fourteen and fifteen"-year-old girls does Edie finally howl "Kissing" to define her level of intimacy with Watters. After Mrs. Peebles says, with relief, "Being intimate means a lot more than that," she tells Edie to go up to her room, and she rejects Alice's offer to perform a medical exam on Edie--"After all, I am a nurse." It is with these calming actions of Mrs. Peebles that the falling action is initiated: "[W]e will not say any more about this."

The falling action continues through Edie's long vigil in the grass at the mailbox. Her unnoticed (by her) flirtation with the mailman, "a Carmichael," continues the falling action. The story is resolved when we are told that, in the years following their marriage, her husband likes to tell the story of how Edie "went after" him by waiting for him every day by the mailbox. Edie doesn't protest. She likes him to be happy.

The plot is structured very simply.  It is told in chronological order.

The plot begins with Edie and Mrs. Peebles rushing outside to look to see if a plane has crashed that they heard overhead a few moments earlier.  A few paragraphs later, the pilot of that Plane, Chris, comes to the Peebles' household and meets Edie.  The plot ends with Chris never writing Edie as he promised and Edie sharing that she fell in love with the mailman who she talked to while waiting on the letters from Chris!  The mailman became her husband:

Edie sums up their entire relationship in the last two sentences of the story, saying they dated for two years and then married. Although they met because she was hoping for a letter from another man, her husband tells their children that she “went after him” by waiting for him every day at the mailbox, and she enjoys his story. (Enotes)