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
Jim can't stand his boss, Professor Welch. But hey, he still has to try to make the old man happy, so he agrees to stay at Welch's house for a boring weekend of music, conversation, and limited booze. At Welch's house, though, he decides that he's got a thing for Christine, the girlfriend of Bertrand, Professor Welch's son. Unfortunately, Jim is sort of committed to another girl named Margaret, who's also staying at Chez Welch.
Act II
Things tend to get pretty bad for Jim after the weekend at the Welches'. Bertrand figures out that Jim's trying to get together with Christine, while Mrs. Welch is out for Jim's blood for burning a giant cigarette hole through her nice bed sheets. All the while, Jim's supposed to be preparing for a big public lecture that'll make or break his career at the university.
The lecture, though, turns out to be a total failure. Jim gets drunk and spends most of the lecture doing an insulting imitation of Professor Welch. Poor Jim ends up losing his job. Meanwhile, Christine has told him that they'll never be together. So Jim's pretty down at the dumps at the end of Act II.
Act III
As bad as everything seems to go in Act II, everything seems just the opposite in Act III. It turns out that Christine's uncle likes Jim's drunken, unpretentious style for some reason, and he gives him the job that Bertrand's been gunning for. And just when things can't get any better, Jim finds out that Christine would like to see him before she leaves.
Jim rushes to the train station and catches Christine just in time (awesome, right?). Christine says maybe they can be together after all, since Jim will be moving to London (where Christine lives) for his new job. The two of them kiss and leave the train station together. As they walk to get lunch somewhere, they pass the Welches, and Jim laughs at all of them. Basically, Jim wins; they lose.