Sig—our narrator and hero—puts his detective skills to the test when his dad winds up dead before the book even starts. Sig's think-on-his-feet ways and quick reflexes help him out a lot in the novel, and it's clear that he's one of those guys who can understand something complicated and break it down into small, simple parts.
In short, Sig's just like his dad. Even Wolff notices this when Sig figures out Wolff's gun is jammed from the cold:
"Smart boy," he said. "Just like your damn father. Too damn smart." (36.25)
Something tells us he's not too happy about Sig's quick intellect. And to be clear, we're not calling Sig a nerd (though we love nerds)—Sig and his pops are the type of smart that comes from experience and figuring stuff out. Neither of them are academic, bookish types—instead, they just get stuff.
Part of this for Sig probably comes from the fact that the kid spends an awful lot of time thinking. He's got nothing better to do up in those below freezing temps, and we're told:
Sig spent much time outside, thinking, thinking, thinking. Trying to work out what to do with himself […] And though he spent much of his time looking, thinking, watching, he could never quite shift the feeling that he was waiting for something. (3.5)
It certainly seems like Sig tries to figure stuff out, doesn't it? Yet he never suspects his dad of anything out of the ordinary—in fact, despite a life spent on the move, he's quite surprised when he learns his dad stole gold from so many people a decade earlier. He looks up to his dad and wants to make him proud, so it comes as quite a blow that Einar wasn't who Sig thought he was. Inclined toward contemplation, though, we're confident Sig will be able to make sense of this doozy—he just needs some time to think it through.
This thoughtfulness may be what inspires him to ask his mom about her religious beliefs. We get the sense that he doesn't buy in to all his mom's talk about her faith, but he doesn't dismiss it outright either. Unlike his dad, Sig tries to think about what his mom would say when times get rough—so though he barely remembers her, he thinks about what she taught him about faith, love, and peace.
And when push comes to shove, Sig tries to honor the memory of his mom by considering what she believed (showing us that he not only loves his mama, but that he respects her too). He tells Anna later that as he was trying to decide whether or not to shoot Wolff in the cabin, he thought:
I suddenly saw what I had to do. I wanted to be true to our mother, but I didn't want to let our father down either. And I saw a way to do both, to make them both happy. (39.28)
Though his mother died when he was very young, it remains important to Sig to consider her perspective on his life as he makes his way through it, in addition to honoring his father. Pretty devoted kid, right? While there are moments when Sig's torn between his parents and what they believe, ultimately he tries to please them both—and luckily for him, this tactic works against Wolff.
When Sig's dad first teaches him about guns, Sig is super excited by it all. He loves hearing about how the gun works and what happens inside the chamber, and it's only later he really thinks about what it means and considers his mom's anti-gun sentiments. When he first shoots the gun, he tells us, "the only frightening thing was how easy it had been, but it would be years before he understood that" (18.57). In other words, though he may be old enough to understand how a gun works and how to fire one, he's not old enough yet to appreciate the stakes.
It isn't until later on that Sig realizes that the gun isn't a toy or something to get so excited by—it can cause very real harm. He never comes to a decision like his parents do about whether guns are always bad (his mom's position) or all-out great (his dad's stance), but he certainly realizes that it's complicated. Perhaps this is one of the reasons he wants to share his story with us in the first place—he wants us to learn about what happened to his family, and maybe even think about guns ourselves.
He closes out the book by saying, "I hope you liked my story" (39.42), and when he does, it's like he's putting us in the driver's seat, relinquishing control of how the story is interpreted. His is a nuanced tale about greed, gold, and guns, and it's up to as now to decide how we'll carry it forward.