Back in the present, it becomes clear why "Thomas" left the codes in the book—to prevent the gangs from understanding its content. He did this because he believed the gangs would eventually come for him after he destroyed their illegal sources of income and contributed to the city's prosperity.
Within the codes, "Thomas" wrote that if he were to die by murder, the gangs would be responsible. And that's exactly what happened—the gangs didn't just kill him, but they killed his entire family as well. They believed they had wiped out every member of his family, including "Adrian." However, as we know, "Adrian" survived.
Now, one might wonder why the gangs didn't return to finish what they started once they discovered "Adrian" was still alive. The answer lies with "Hansen." Once he realized what had happened, he knew the gangs would eventually come back for "Adrian." To protect him, "Hansen" faked "Adrian's" death, publicly announcing that all members of "Thomas'" family had perished.
But how did "Hansen" pull off this deception?
The funeral proceedings were kept secret. "Hansen" and "Patrick" declared that the burial would be held at an unexpected time with no public attendance, fearing something might happen to the bodies. But all of that was a lie. The true intention was to keep the fact that "Adrian" was still alive hidden from everyone.
But "Hansen" and "Patrick" didn't stop at just changing the funeral arrangements. They also changed "Adrian's" name. His real name was "Heinz Aiven", not "Adrian Aiven."
However, simply changing his name wasn't enough to completely hide his identity. This is where "Patrick," a skilled surgeon, came in. He made a scar on "Heinz's" face to completely alter his appearance, making him look like a completely different person named "Adrian."
As for "Gary," his father had been a close friend of "Thomas" and was fully aware of the truth behind "Heinz's" identity and the drastic changes that had been made.