It's not that long after his expulsion that Clif Clawson shows back up in Martin's life driving a nice new car. Turns out that Clif's gift for gab has made him a very good car salesman.
He drives Martin into Zenith and buys him a nice lunch. They're joined by a dude named George F. Babbitt. Fun fact: Babbitt is actually the fictional protagonist of another Sinclair Lewis novel called (wait for it) Babbitt. Lewis had a way of making the characters and places in his novels overlap like this.
Martin returns home from the lunch feeling like he's a poor, miserable failure. A letter from Leora saying that she won't be back in town for quite a while makes him feel even worse.
He starts drinking more and neglecting some of his courses. He even lands himself in the office of the Dean, who expresses concern over Arrowsmith's falling quality of work and his rudeness to professors.
Martin is too frustrated to apologize for anything, so instead he ends up getting himself suspended from medical school. The dean tells him he's welcome back as soon as he's ready to apologize and straighten out his life.
When he leaves, Martin asks Clif Clawson for a hundred dollars, which was a lot of money in Sinclair Lewis' time. Clif is a good pal, though, and he gets him the money.
Martin uses the money to wander around the United States for a bit and finally go to Leora's hometown to see her. He tells her immediately that he's been suspended from school, but she doesn't really care as long as they're together.
Meeting Leora's family is a bit of a strain. They're very controlling, and ask a lot of nosy questions about how Martin plans on making his living. Needless to say that he doesn't come out and tell them he's been suspended from school. Leora's brother Bertie is especially harsh when it comes to grilling Martin.
Martin and Leora decide to run away from her family and get married without their permission. When they return to Leora's hometown, the whole family is waiting for them at the train station. They're totally livid, but they have to accept that the lovebirds are married.
The family, however, insists that Martin and Leora aren't allowed to "act" as if they're married until Martin is settled in a job. And by this, of course, they mean that Martin and Leora aren't allowed to sleep in the same bed or have sex.
That's a huge motivation. Three days later, Martin walks back into the office of his med school dean and begs to be let back in.