After accidentally time-traveling to 1982 New York City, Phineas Bogg teams up with 11-year-old Jeffrey Jones to fix errors in the space-time continuum that have changed the course of history.

While in ancient Rome, Phineas duels Spartacus in a gladiator match; he and Jeffrey then escape to Hannibal, Missouri, where Harriet Tubman is fleeing for her life.

Phineas and Jeffrey attempt to save Theodore Roosevelt from being killed by Billy the Kid; they also pay a visit to Benjamin Franklin and assist him with an iconic experiment.

In colonial Massachusetts, Phineas and Jeffrey find themselves among the Salem witch trials, where they are accused of witchcraft.

Phineas and Jeffrey become separated in the early-1900s Middle East; Phineas is captured with Lawrence of Arabia, and Jeffrey escapes to New Jersey and finds Thomas Edison.

A trip to Rome introduces Phineas and Jeffrey to Cleopatra, but they accidentally transport her to 1920s New York, where she crosses paths with Babe Ruth.