

In the books, Saruman and Wormtongue escape from Isengard and set up shop in the Shire while the hobbits are still busy wrapping things up in Gondor and Rivendell. They turn the Shire into an industrialized dystopia, destroying the environment and subverting the local hobbits with promises of wealth and power before betraying them and turning them against each other. (Basically, what Frodo sees in the film adaptation when he looks in the Mirror of Galadriel.)
When Frodo & co. return, they organize an underground resistance movement that escalates into a popular revolution.







There would be continuity issues with Jackson’s adaptation, too—in the films, Saruman and Wormtongue die at Isengard (in the extended edition), Galadriel says Frodo’s dystopian vision of the Shire is what will happen if he fails, Rosie Cotton is a barmaid instead of a fellow member of Sam’s agrarian resistance cell, Odo Proudfoot and the rest of Hobbiton are visibly unchanged when the hobbits arrive, etc.