Marty makes an emergency trip back to Salem, Massachusetts in the DeLorean to deliver a spare flux capacitor to Doc and the family. While Doc installs it to fix the train, Marty, Clara and the boys go into town, where Marty gets accused of being a witch.

Marty, Jules and Verne head back to the 1850s, where they meet Jules and Verne's maternal grandparents, Daniel and Martha. Unfortunately, Martha falls in love with Marty instead of Daniel, and Clara is in danger of never existing. Things get worse when Martha is kidnapped by Wild Bill Tannen...

On a trip to the 1940s, Verne enters a dance contest with his future dance instructor, Dorothy, while Marty gets drafted.

Verne and his new friend, Chris, go see a 1930s circus, which the owners are about to lose to landlord Farmer Tannen.

After finding a strange craft in Doc's bushes, Biff claims Doc is an alien and everyone believes him. In 1967, Marty, Jules and Verne arrive to discover the truth.