In October of 1944, Ted Hall goes home to celebrate his nineteenth birthday.
While there he hooks up with his old roommate Saville Sax, who is still pretty into the whole communism thing.
Hall asks Sax how he should go about giving information to the Soviets, but Sax is equally clueless.
They decide to walk into a Soviet import/export business and ask for someone to give top-secret information to—which is a pretty naïve plan. The guy they talk to there is like, "You idiots realize that the FBI is watching the joint, right?" but he refers them to Sergei Kurnakov, who is a Soviet journalist from New York.
When they meet with Kurnakov, he can hardly believe this pimply, awkward kid could be a physicist working for the U.S. government, but then Hall hands him a folder with everything they've already figured out about building an atomic bomb.
Since Hall will be mostly incommunicado while at Los Alamos, he suggests Sax act as a courier between him and Kurnakov.
The KGB are pretty psyched to finally have an agent in Los Alamos to relay information to them.
Meanwhile, Gold and Yatzkov are still trying to locate the missing Fuchs. They track down his sister, and she reveals that he was transferred somewhere in the Southwest United States but should be home (and probably able to contact them) sometime around Christmas.
Fuchs is indeed in the Southwest—he and the British team were called up to the big leagues at Los Alamos.
He's an important part of the Los Alamos team, but he always seems to be on the periphery of the social scene. Fuchs's only friend is Feynman, who scolds him for missing out on all the fun in life. However, he's still much liked and is a popular babysitter amongst the people at Los Alamos.