Picking up where #2 left off, Marty is stuck in 1955 again and has to explain to the 1955 Doc why he's back and uses a letter Doc sends him from 1885 to explain what happened. After fixing up the time machine (hidden in a from 1885 cave), they find out that Doc is murdered in the past by Buford "Mad Dog" Tannen (played by Thomas F. Wilson) "over a matter of $80 dollars." So Marty decides to go back and rescue Doc before the murder can occur, but he is bedeviled by a rip in the fuel line - meaning they have to find another way to get the time machine to hit 88 miles per hour - and Doc falling in love with school teacher Clara Clayton (Mary Steenburgen). Along the way, he gets advice both from Doc and his 1885 ancestor Seamus McFly (also played by Michael J. Fox) that he should really learn to control his temper.
Fox and Lloyd are fun to watch as always, and I give my hat off to the studio for hiring Mary Steenburgen as Doc's love interest and not some super model type; it's more fitting of who Doc is. Wilson's Biff Tannen officially became a traditional "villain" in #2 with him murdering George McFly, and now Wilson plays an even bigger villain in Buford Tannen, whom he makes both funny and menacing.
Ironically, Wilson is said to be a very nice man in real life. Leah Thompson makes the most of a thankless dual role as both Lorraine McFly and Marty's great, great grandmother Maggie McFly, and James Tolkan plays his Principal character's soft spoken law man ancestor (killed in a deleted scene by Buford Tannen; "Remember son... discipline.")
It should be noted that originally there were no sequels planned with the first movie; that bit with Doc taking Marty and Jennifer to the future to help their kids was just another gag. But the film was such a hit that the studio couldn't NOT do sequels, so this one and part 2 were filmed back to back, which is becoming more of a craze these days.
Although on the surface it's a lighthearted comedy about time travel, it's also about what it means to be a man. The first film defined being a man through violently standing up to your tormentors, while this film and #2 go with the theme that being a man also means you have to reign yourself in when people start annoying you. Marty' willingness to fight back was his strength in the first film but here it is his flaw, as people in both 2015, 1955 and 1885 continually get his goat. The message of self-control is bluntly stated when Doc says to Marty "You can' t keep going off the handle every time someone calls you a name, that's why you get into that accident in the future!" (referring of course to the car accident mentioned in part 2). It is not until Marty realizes his error when he's about to meet Buford in the gun fight that he achieves this ideal and, much to Seamus's glee, says of Buford and the opinions surrounding him "He's an asshole! I don't care what Tannen says, and I don't care what anyone else says either!" Because of this, he is able to avoid said accident.
Also loaded with gags, references to other great westerns ("My name is Clint Eastwood.") and Doc's response to being asked if his hijacking the train is a hold up: "It's a science experiment!"
