Toby Wolff lives with his mother, a flighty woman constantly looking for new beginnings. She also has a habit of attracting crazy men, violent men or some delightful combination of the two. She and Toby move to Utah to prospect for uranium, but can't find any. They also get a surprise visit from mom's ex-boyfriend Roy, who plays house with them and buys Toby a Winchester rifle in between vague acts of menace. In the meantime, Toby changes his name to "Jack," because he thinks it sounds cool.
They eventually dump Roy and head for Seattle, almost on a whim. Mom joins forces with another pair of single women, while Jack proceeds to become a troublemaker. The other women try to fix Jack's mom up with a husband. She eventually settles on Dwight, a seemingly nice man trying way too hard. He lives in a little town north of Seattle and brings them up to live with him. Dwight turns out to be quite a monster. He drinks and drives—always a sign of class—spends money on himself at the expense of others, and often resorts to physical abuse.
The bulk of the book is given over to life with Dwight. Jack searches for rules and order by joining the Boy Scouts, but Dwight ruins that by making himself an assistant Scoutmaster. Dwight ruins a lot of things, much of which Jack's mom never sees. Despite Jack's need to be a part of a world that makes sense, he continues his screw-up ways: engaging in petty crime, hanging out with no-goodniks, and generally playing the bad boy. Dwight's attempts to "make a man" out of him don't help.
He makes friends with an effeminate boy named Arthur Gayle, who seems to need a buddy, and fantasizes about running away. He never has the guts to do it, but he does write his distant relatives begging for help. His uncle offers to let him come live in Paris with him, but it would mean getting adopted by his Uncle and Jack just loves his momma too much. Possible salvation also arises in the form of a private school scholarship. Jack lies on his applications, but still scores a scholarship to Hill. In the process, he discovers that lying and writing are actually kind of the same… and he loves it.
Things finally come to a head with Dwight when he pushes Jack down and Jack lands on an already injured hand. Yeah, no good. He lives with the family of a friend for a few months, though his wild ways continue. He and his friend drink, stay out late, and steal gas before Jack finally heads to Seattle to be a Good Little Prep School Boy.
That, of course, doesn't happen. He spends the summer with his dad—who straight up gets committed to a lunatic asylum—and dodges the skeezy advances of a pedophile sent to look after him. His mom moves to Washington DC while he goes to prep school, but Dwight catches up to her and tries to strangle her in their apartment building. That's pretty much the end of Dwight. Jack doesn't do well in prep school and gets kicked out his senior year. He joins the army instead, and gets shipped off to Vietnam, which sounds a little daunting. For that story, you have to read the action-packed sequel In Pharaoh's Army.