Phineas Bogg is a member of a group time travelers called Voyagers. He is a regular human that once lived as a pirate before he was chosen to be a voyager. He travels by way of a brass pocket watch type device called an omni. When the light flashes red, it means history is wrong. His job is to fix it. When he does the omni light rings green. The show offers glimpses into alternate universes where history has run afoul.
In the pilot episode, Bogg ends up in 1982 when his omni malfunctions. (His omni parameters only go as far as 1970.) He ends up in the apartment where 11 year old Jeffrey Jones and his aunt and uncle. (Jones' parents were recently killed in an accident.) Jeffrey feels unwanted and lonely. After Bogg crashes through his window, Jeffrey's dog grabs hold of Bogg's Guidebook. (A special history book) Bogg struggles for the book and Jeffrey falls out of the building's window. They are 30 stories up! The only Bogg jumps out after him and activates the omni.
Now Bogg is stuck in time with Jeffrey, no guidebook, and no way of getting Jeffrey back to his own time. But he does have an ace in the hole. Jeffrey's dad was a history professor and Jeffery picked up much of his knowledge. Bogg is pretty inept with history and has no clue what to do without his book. The two bond and become friends, and eventually love each other like a real family. For twenty adventure filled episodes, the two travel through time giving history a push where it's needed.