John Fitzgerald shows us the darker side of frontier life. A gambler and murderer by trade—tough racket—Fitzgerald came out west to escape life and all the mistakes he made along the way. Too bad he ends up making the biggest mistake of all time by turning his back on Hugh Glass.
We'll be real: Fitzgerald isn't that complex of a character. Although he came from a decent New Orleans family, he "demonstrated both a reflex toward and a skill for engaging in violence" from a young age (1.5.10). That's a bad start. He eventually bails on New Orleans after killing a prostitute he's in love with and finally ends up in Memphis, where he becomes a degenerate gambler. In fact, he only heads out West in the first place because he owes thousands to local bookies.
In an unfortunate twist, Fitzgerald finds his nasty qualities rewarded on the frontier. He might be lazy and untrustworthy, but he's a tough fighter who can keep his cool in a battle—and that's a lot harder to come by out in the West than you might think. While "many of Henry's men had been terrified in their fights with various Indians [...] Fitzgerald found them exhilarating, even titillating" (1.5.20).
But Fitzgerald trips up when he applies his violent, greedy mindset to Hugh Glass. Eager to get his grimy hands on Glass's prized Anstadt, Fitzgerald initially plans on straight up murdering him, but he eventually decides to just steal his gun and run away. It's not a complicated plan. Ever the gambler, Fitzgerald doubles-down by stealing a grip of beaver pelts from Captain Henry and deserting the Rocky Mountain Fur Company for good.
Then, through a bizarre turn of events, Fitzgerald ends up in the Army. Although he joined the military simply because jail was his only other option, Fitzgerald is more than happy to use his status as a G.I. to evade Glass, lying in military court that Glass's revenge quest is nothing more than a delirium-induced hallucination. And his plan would have worked if it weren't for that meddling Glass, who pulls out his gun and shoots old Fitzy right in the shoulder in the middle of the trial.
Did we mention that Glass was actually aiming for Fitzgerald's heart?
So what's next for Fitzgerald? The end of the novel signals that Glass is letting go of his revenge quest, so Fitzy shouldn't have to worry about the revenant coming after him again. Still, we'd be hard pressed to imagine a happy ending for a guy as nasty as Fitzgerald in a place as dangerous as the frontier, even considering how kind the frontier can be to nasty people like him.