Before we meet Seymour, we hear that there's something wrong with him. Salinger uses Muriel's conversation with her mother to preface Seymour's interaction with Sybil. We have to do a pretty careful job of reading between the lines here to figure out what's up; very little is explicit or obvious, so we infer and deduce the scenario by looking at little hints.
Muriel's mom asks over and over again if Muriel is safe and if Seymour is behaving himself. Her references to Seymour's behavior in the past – funny business with trees, inappropriate comments about death, something to do with a window – all suggest that Seymour is emotionally unstable. We even gather that he intentionally drove a car into a tree. When Muriel's mother mentions a Dr. Sivetski, we know that they've gotten Seymour into psychotherapy. And then comes the big warning: "There's a chance – a very great chance, he said – that Seymour may completely lose control of himself" (51).
This should worry us a little bit, or at least raise our concern for Seymour. But Muriel is so cavalier about her husband's condition that our fears are somewhat put to rest. Perhaps this is just a case of an overanxious, overprotective mother who doesn't really like her son-in-law?
Then again, perhaps not. We do get a bit more information before we head on to scene number two. We find out that Seymour has only recently come back from the war (World War II, as this is 1948), and that he spent some time in army hospital – presumably for whatever mental or emotional troubles he's still experiencing now – before coming home. Now we're thinking along the lines of PTSD, or post-traumatic stress disorder. Today, the world is well-informed about this condition, and most people are sensitive to it. But in the 1940s, when Salinger was writing, PTSD wasn't really a buzz-word yet. (The phrase wasn't even coined until the 1970s.) So instead of trying to help or understand Seymour, most people are reacting to him in the same way as Muriel's mother. They think he's weird, and they'd rather just avoid him at all costs.
And so the stage is set, all before we meet our main character. What happens when we actually do encounter Seymour? Let's consider his interaction with Sybil. For starters, he's funny. He's engaging, entertaining, kind, and obviously amazing with children. He plays with Sybil and even tries to teach her a lesson or two (as when he gently reprimands her for teasing the dogs in the hotel lobby).
But there's more to this scene. For starters, Seymour is alone on a deserted part of the beach. He's isolated himself from other adults and comes off as something of a loner. Before Sybil comes along, he's lying down in a tightly cinched-up bathrobe, which strikes us as a bit odd for a tourist on a beach in Florida.
Then, of course, we have to consider the nature of his interaction with Sybil. Jaded and cynical readers will want to know why a grown man has chosen to cultivate a friendship with a four-year-old girl while snubbing adult society. They might even suspect that there's a shade of pedophilia in his relationship with her. (Critics are definitely divided on this topic. See "Sex" for a full discussion of the ambiguity.) What we do know is that Sybil's relationship with Seymour is hugely important to this story – which we'll discuss in Sybil's "Character Analysis." We also know that their conversation is potentially loaded with hidden meaning, metaphor, and symbols, which we explore in "Symbols, Imagery, Allegory."
Back to Seymour. After the scene with Sybil, we're still not really sure about his mental health. Maybe he is mentally unstable, or maybe he's just a loner who happens to love children and has been completely misinterpreted by more materialistic people like Muriel's mom.
But we're done guessing after the elevator scene. Seymour, for no apparent reason, accuses a woman of staring at his feet, calling her a "god-damned sneak" (104). He then goes into his room and kills himself. Now we know for sure – Seymour is unstable.
Which brings us to the big question: why does Seymour kill himself? There is no one answer to this question, but we discuss many different options in "What's Up with the Ending?" It's also possible that there is no answer, which we discuss in "What's Up with the Epigraph."