On the eve of the year 2000, Edmond Blackadder is entertaining his friends in his family castle, and announces that he has built a time machine. He gets them each to agree to a bet, whether he can or cannot bring to the future certain objects from history, of their choosing. They name a Roman helmet, Wellington's Wellingtons from Waterloo, and a pair of two hundred year old dirty underpants. Blackadder is always a scoundrel, and has devised an elaborate cheat. He had Baldrick precisely follow plans for a time machine in one of Leonardo Da Vinci's notebooks, but has no expectation that this will work. Instead, there is a trap door in the bottom, and he intends to enter the box that is the machine, have Baldrick bring him objects fitting the descriptions, and then emerge a moment later claiming to have been gone for a long time but to have returned to the same moment, and claim his winnings. Unfortunately for him, Da Vinci's time machine actually works; also unfortunately, Baldrick never marked the controls with their original starting position, so they cannot simply return to the right time. However, as often happens for the Edmond Blackadders of history, the comedy of errors works very much in his favor, as he wanders through time disrupting history completely and returns to claim his winnings.
It is an incidental pet peeve that they say it is the eve of a new century and a new millennium. The year 2000 was actually the last year of the twentieth century and the second millennium; the first year of the new ones was 2001. But it was a common misconception of the time. However, it gives us a secure starting date.
To sketch events briefly, the duo leaps back to the Jurassic era, where they use their fake trophies to fend off a tyrannosaurus. The second stop is the court of Elizabeth I (who reigned 1558 through 1603, but is young here), then forward to a future in which spacefighters are shooting at each other, back to Robin Hood (a fictional character, but the events of his story are fixed to the period of 1195 to 1200 when Richard I was a prisoner), then to the Battle of Waterloo (Sunday 18 June 1815), then to the withdrawal of Roman troops from Rome by Emperor Hadrian (who became Emperor August 117 and had Hadrian's Wall built beginning in 122; however, he never withdrew troops from Britain, who remained there until the late fourth or early fifth century), and then home. He finds that he has altered history in ways he finds unacceptable, and so launches a second mission in which he attempts to repair the damage. We see brief visits to the same moments already visited at Waterloo, Sherwood, and Elizabethan England, and then he returns to find everything restored to normal. Melchett then comments that an unscrupulous individual with such power might make serious changes to history, and Blackadder excuses himself once more for one more trip. We do not know where he goes or what he does, but we do know the outcome, as he once more changes history.
With all the changes to history, we can safely say that this is not a fixed time theory story. Thus as we watch the changes and the travels we will attempt to determine whether this movie works under any theory of time.