Usually Part 2 isn't a favourite with most people, but I like the complexity of it. Lots more time travel, technology, and general mind-bending-ness appeals to my inner geek. The effects are an impressive leap beyond the previous installment, and the different versions of Hill Valley are very well done. It's interesting to see the town evolve through the different time periods. Also, the actors playing different characters is well done - although Michael J Fox playing his daughter is disturbing. Revisiting 1955 is cleverly done, with previous events shown again from different perspectives, with other versions of characters interacting within it. An excellent installment to the series.

Plot Synopsis:

Marty has returned home from 1955 to find his future improved. He meets with Jennifer, but is interrupted when Doc Brown returns from the future in a modified Delorean. It no longer relies on nuclear power, running instead on rubbish and the Mr Fusion power generator. Doc tells Marty he has to come back to the future because somethings wrong with his kids. He tells her to bring Jennifer with them. They leave in the Delorean, and it flies away into the future (Doc has also had the car hover-converted). Biff comes outside and see's the car leave for the future.

Marty, Doc and Jennifer arrive in 2015. Doc tranquilizes Jennifer, who is not necessary for his plan, explaining that he brought her along only because she saw the time machine. Doc explains that Marty's son is about to be approached by Griff Tannen, Biff's grandson, and his gang, who will ask him to take part in a robbery. According to Doc, this event leads to the ruin of the entire McFly family. Marty replaces his son and tells Griff he will not join the robbery, leading to a hoverboard chase that damages the nearby courthouse, and causes Griff and his gang to be arrested. This stops the robbery from ever taking place.

Learning the Cubs have won the World Series, Marty purchases a sports almanac covering all sports statistics from 1950 to 2000, so he can bet on future games with certainty and become wealthy. Doc discovers the almanac and throws it away, telling Marty that he did not invent time travel for financial gain. Old Biff overhears the conversation about the almanac and the time machine, and having seen the Delorean before in 1985 figures out what's going on.

Jennifer, still tranquilized, is found by the police, mistaken for her future self after thumbprint identification, and taken to her future home. Hiding in a closet, she witnesses the Marty of 2015 being fired from his job when his boss catches him in an illegal scheme that a colleague (formerly a schoolmate) goaded him into joining. Doc finds Jennifer sneaking her out of the house after she briefly meets her future self, causing both to faint in shock.

While Doc is rescuing Jennifer, the old-aged Biff of 2015 recovers the discarded sports almanac and steals the Delorean. He returns the car to 2015 just as Marty and Doc prepare to leave for their own time. Upon arrival in 1985, Marty and Doc find that Hill Valley has become a crime-ridden slum lorded over by a middle-aged Biff, who is now immeasurably rich and powerful and married to Marty's widowed mother, Lorraine. Doc deduces that the Biff of 2015 must have given the almanac to his younger self sometime in the past. Marty confronts Biff and finds out that he received the almanac on November 12, 1955 from a mysterious old man. Biff then tries to kill Marty, being forewarned by Old Biff that a kid might come looking for the book one day. With the help of Doc, Marty escapes Biff's Pleasure Palace.

Doc later speculates that this date could be a point that has a special significance to the space-time continuum, or that it "might be a huge coincidence." Marty and Doc travel back to 1955 to prevent the corrupted 1985 from happening. Marty eventually manages to steal the almanac from the 1955 Biff, while trying to avoid running into the other versions of himself and Doc in 1955.

When he is no longer in any danger of having it taken by Biff, Marty burns the almanac, restoring history to its proper course. As Doc attempts to land the Delorean, the car is struck by lightning, and it time travels in error. It is sent back to 1885 due to a malfunction in the time circuits.

A few seconds later a Western Union delivery man appears with a letter, which he explains was given to them seventy years ago with the explicit instructions that it be delivered to Marty "at this exact location, at this exact minute, November 12, 1955." Marty tears open the letter, which is from Doc, explaining that he is now trapped in 1885.

Marty locates the Doc of 1955, who is at the clock tower sending Marty back to 1985. After the time machine vanishes, Marty then appears to Doc, who faints when he sees that Marty has come "back from the future". Marty tries to revive Doc as the text TO BE CONCLUDED appears.

This is followed by a teaser to Back to the Future Part 3.