Tom and Maggie Tulliver are two kids growing up at Dorlcote Mill, which has been in their family for generations. The kids have a lot of extended family living nearby, and their aunts and uncles frequently come by to argue amongst themselves and to scold Tom and Maggie. The Tulliver kids have a stormy relationship. They spend most of their time getting along really well or else fighting horribly. Maggie in particular is very smart and very emotional and is always getting into trouble.
Two major things are in the works for the Tullivers: school and a lawsuit. Tom and Maggie are both sent to schools and Tom gets a fancy, if useless, education. While at school he meets a deformed boy named Philip Wakem, who is the son of Mr. Tulliver’s arch-nemesis. Mr. Tulliver dislikes Mr. Wakem, a lawyer, since he is involved in a lawsuit against one of Wakem’s clients. Mr. Tulliver loses his lawsuit and things go rapidly downhill for the Tulliver family. They go bankrupt and Mr. Tulliver’s health begins to fail. Mr. Wakem buys the Tulliver family mill, which causes Mr. Tulliver to hate the Wakems even more and to curse them in the family Bible.
After the lawsuit fiasco, the Tulliver kids are forced to leave school and start working. Tom slaves away for one of his uncles and is obsessed with paying off the family debts. Maggie finds comfort in an extreme form of religion, but she later puts that aside in favor of a secret friendship with Philip Wakem, who has been in love with Maggie ever since they first met. Maggie’s passionate nature continues to cause her a lot of emotional distress.
Tom discovers Maggie’s relationship with Philip and forbids her from seeing him again. Maggie is torn but decides that family loyalty comes first. Her relationship with Tom is badly damaged. Shortly after this, Tom manages to pay off the family debts, but the triumph is ruined when Mr. Tulliver attacks Mr. Wakem and then dies shortly afterwards. The Tullivers must move away from the mill.
A few years go by and Maggie returns from a stint as a governess to stay with her cousin Lucy. Tom has worked his way up in his uncle’s business and is now successful. Maggie meets Stephen Guest, Lucy’s boyfriend, and the two quickly fall in love. Philip also returns and Maggie is embroiled in a messy love quadrangle. Eventually, Stephen and Maggie are unable to control their feelings and the two try to elope. But Maggie has a crisis of conscience and leaves Stephen, returning home in disgrace.
Though Maggie reconciles with those closest to her, she is unable to make amends with the judgmental Tom. After a period of intense emotional suffering for Maggie, the local river floods. Maggie goes to rescue Tom and the two reconcile their differences. But Tom and Maggie are drowned in the flood. The other characters all survive and move on with their lives and Tom and Maggie are buried together.