I’ve just watched it. I’m always in two minds about this one. One the one hand, this doesn’t have the same level of character focus as the first and third, so it’s harder to care what’s happening, but on the other, there is so much going on in it, there’s more time travel doings than in both of the others combined, so it’s just as hard to look away for fear you’ll miss something.
It’s more like a series of shorts that build up, really. First we go to the future - sadly now even 2015 is in the past of course! - because Doc has seen what happens to Marty’s family. This leads to some fun capers, but also a major plot hole. During the 2015 sequence, we hear about the Rolls Royce incident that wrecked Marty’s career, why didn’t Doc just warn Marty about that instead? (Because of course that would have meant we didn’t get all the fun and action and suspense of parts 2 and 3!) And then of course old Biff appears on the scene, and by 2015, he’s actually developed some brains. He realises the potential of the time machine, and goes back to make himself rich. This Biff is the most dangerous of them all, because he really knows what to do and how to do it.
So the return to 1985, and we’re thinking, “that was fast”, only to find that things are not as they should be. Old Biff has really done a lot of good for himself - and a lot of bad for everybody else. He even warned his younger self about Marty and Doc. So Marty finds out exactly when Biff got his hands on that sports almanac, and in so doing, the creators gave themselves a unique opportunity to break the fourth wall in the original movie, by interacting with the events of it - in some cases actually reusing the original footage.
Yes, it’s back to 1955 again, and this is one thing that I always forget when watching the first one. These events from part 2 are happening around it! A very effective idea, because not only are they trying to restore their original timeline of 1985, they have to avoid messing things up here in 1955! The whole thing is very cleverly done, and the whole sense of relief as the newspapers change at the end makes up slightly for the lack of character focus.
But suddenly, just when it looks like that’s the end, Doc gets zapped back in time! Marty is trapped in 1955, until he receives the letter. The guy asking him if he needs any help is a little contrived, but it was necessary for the response, “there’s only one man who can help me!” - Doc’s 1955 counterpart. And cut to the end of the previous movie. It doesn’t have the same suspense here as it did originally, because we already know what’s going to happen because it’s already happened in our perception of the story. And suddenly Marty appears again, and Doc, understandably, is in a state of shock. Setting things up nicely for the finale - the trailer for which is included at the end as part of this movie, and very tantalising it looks too!
But as a kid I found the alternate 1985 and many of the 2015 scenes to be quite disturbing. Just the “evilness” of everything was a bit unnerving. I guess that’s why I didn’t watch this one as much as I did parts I and III.