For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
Everyone starts a new project: Tagomi thinks he's starting a new trade mission with Baynes; Baynes comes with his secret mission; Frank starts his new business; Juliana finds a new guy; and Childan worries about his old way of business (and starts to make friends with the Kasouras).
Act II
Everyone's project goes horribly wrong: Tagomi's trade mission turns out to be a secret plan; Baynes gets attacked by Germans; Frank's business goes nowhere and he gets arrested; Juliana realizes her guy Joe is an assassin; and Childan realizes his friendship with the Kasouras (or rather, attempted seduction of Betty) leads him to a huge dilemma about the American jewelry he has to sell.
Act III
Everything turns out OK: Tagomi falls into a terrible alternate history and takes a stand against Nazi Germany by refusing to send Frank Frink to his death; Baynes succeeds and goes home; Frank is released and goes back to work; Juliana finds out from Hawthorne Abendsen that his book tells the truth; and Childan stands up for American art.