Marketing tells us that Jyn Erso is the brave and hopeful heroine at the center of Rogue One: A Star Wars Story, the first official Star Wars spin-off film, but with a month to go before the film hits theaters, we barely know anything about her. Luckily, it’s said that you can know a person by the company they keep, and the latest prequel novel shows us how Jyn’s past will likely affect her future.

The new book Rogue One: Catalyst, which was released last week, includes the story of Galen and Lyra Erso right around when Jyn is born. The book dives into the events immediately preceding and following “Order 66,” when the Republic was transformed into the Empire, but the main focus is on this one family. In particular, we hone in on Galen, who’s the most important man in the galaxy.

That’s not an exaggeration. For a time, Galen is the most sought-after man in the entire war. His research into kyber crystals hints at unlocking a massive energy source. He wants to use it for good, but both sides of the war are determined to use it for their own ends. Unfortunately for them, Galen is a pacifist, refusing to help the Republic or the Separatists despite being promised glory or threatened with imprisonment if he doesn’t comply. He even punches out a scientific rival who suggests Galen is a traitor for not helping the cause.

“I would guess you would call him a conscientious objector rather than a conscientious collaborator. He wants no part of it,” author James Luceno said in an interview. “This, of course, makes him suspect to not only military members of the Republic but his own peers in the scientific community. They wonder why he is not volunteering his vast talent for the war effort since so many of them are.”

After the war is over, Galen’s college friend Orson Krennic (played by Ben Mendelsohn Rogue One) cons him into helping the Empire under the guise of supplying energy to recovering worlds. You see Galen’s stubborn streak continue as he dives deeper into kyber crystal research, determined to unlock their mystery at any cost (including his relationship). It’s not until Galen is presented with convincing evidence that the Empire is playing him that he is able to break out of the trance and recognize just how much damage he’s done. By then, it’s too late. Galen’s single-minded focus and stubborn streak have shown the Empire the path to the Death Star, likely leading to Galen’s later capture in Rogue One to finish the work he started.

There is evidence that the entire Erso family is Force-sensitive, though none of them appear to have the abilities to wield it. The crystals (imbibed with the Force) change Galen psychologically when he’s working on them, affecting his sleeping patterns and giving him complex dreams. You’ve also got Lyra Erso, who mourns the loss of the Jedi as an attack on the Force itself.

Lyra is essentially Galen’s opposite, and both of them understand that. While Galen is focused and single-minded, Lyra is a curious explorer who revels in the forces of nature. She’s been described as a “Force hippie,” but that’s kind of inaccurate. Her adulation of the Force comes from a profound respect for the diversity of life, and she accepts that there are some things that are (and should be) beyond our knowledge. After seeing proof that the Empire is mining previously protected planets for resources, Lyra’s the one who convinces Galen that something is seriously wrong with Project Celestial Power, the cover for the Death Star construction.

The book does a great job at showing just how much Jyn takes after her parents, and how much their actions have influenced her. Jyn’s adventuring spirit is inherited from her mother at an early age (along with most of her looks), but she’s also stubborn as hell with a tenacity for scientific discovery like her father. There’s one scene where Jyn is drawing a picture of her father as a fictional character from her favorite holovid, and there are doodles of the same mathematical equations that Galen has been experimenting with. Jyn also shows an affinity for kyber crystals, declaring she “wants one” upon first sighting. Lucky for her, she later gets one, as we saw in one of the Rogue One trailers.

In the end, Catalyst shows us how the lives and mistakes of Jyn’s parents (particularly her father) have shaped the kind of person Jyn will become in Rogue One. Galen helped give the Empire one of the most dangerous weapons in the Star Wars universe, but it was while he was trying to make the universe a better place. He failed to listen to those around him until it was too late, and he’s now culpable in the murder of billions of people. It’s a mistake his daughter will struggle to amend, and she could end up paying the ultimate price for it.

Beth Elderkin is a freelance journalist and producer based in Chicago. She works as weekend editor for io9 and co-hosts TV review series Shark Jumping on Channel Awesome.