Sig finds his dad dead out on the ice and—understandably—wants to learn more about how he died. So Sig starts using clues his dad left him to piece together the mystery of his death. A Bible here, a match there, a frozen-over patch in the ice—it looks like Sig's dad, Einar, froze to death out on the arctic lake. Sig's not sure why his dad would even go out there, but before he can think about it more, a mysterious stranger shows up at the house, wanting to talk to Einar.
The guy's name is Wolff and let's just say he's scary looking. Sig wishes his sister, Anna, would come back with his stepmom, Nadya, because they'd know what to do—but before they return, Wolff tells Sig that his dad owes him half of his gold. None of this makes sense to Sig. He knows his dad isn't rich and never has been. Sure, they've moved around a lot in the past ten years, but they've never had money.
Through some flashbacks to ten years before, we learn that Sig's mom, Maria, was a God-fearing woman who brought out the best in Einar but argued with him over weapons. When Einar buys a gun, she goes ballistic—this is one thing that Maria and Einar can't seem to agree on, no matter how hard they try. Sig for one, thinks that his dad is right that the gun is beautiful and really well designed, but he also sees his mom's point that is can hurt people.
His dad is an assayer (read: he measures and evaluates people's gold) in the city and works really hard. One day, he gets a visit from a creepy man with no thumb—a.k.a Wolff—who makes Einar a proposition: he will not tell anyone Einar is stealing everyone's gold if he splits it with Wolff down the middle.
Einar says he's not sure what the guy's talking about, and decides to skip town soon. One day, Sig sees just how much damage a gun can do when he comes home to find his mom killed. Everyone is devastated, and later, Anna tells Sig that Wolff is the guy who did it. Uh-oh.
Back in the present, Sig gets more scared when Anna comes home without Nadya and knows exactly who Wolff is—she doesn't know anything about any gold though. Wolff aims the gun at Sig and—just then—he remembers something. When he found his dad's body, there were papers next to it from his desk. Sig didn't think anything of it at the time, but maybe they can tell them where the gold is. Wolff isn't sure whether he buys it, but he goes along with it anyway.
Sig takes the guy out to the icy lake and they grab his dad's stuff. Suddenly, Sig really wants his mom's Bible since that's the only thing he has left of her. The bad news is that Wolff doesn't find what he's looking for in the papers, and tries to hurt Anna to get more information. Sig distracts Wolff and sends Anna out to get help, then runs after her. A gunshot rings out, but luckily Wolff has hit only his own hand. As he comes chasing after the siblings, help finally arrives, and Wolff is arrested and taken away.
Later, Sig finds a letter from his dad in the Bible, along with a map to the gold—it turns out his dad did steal gold from people, and they've been running ever since. Sig's not sure how to feel about his dad being a thief, but he decides to invest the gold in the iron mine to prepare for his family's future. Fifty years later, he tells us that Wolff died in a prison brawl. Meanwhile, Sig decided to write down his story so other people could read it too—and this is the book we've been reading this whole time. He hopes we liked it (thanks, Sig).