Back to The Future trilogy was created by Steven Spielberg and Rob Zemeckis. It is about time travel. Dr. Emmett Brown converts a DeLorean into a time machine using the famous flux capacitor. He wants Marty McFly to see his creation.
Marty ends up in 1955 when he takes the car up to the speed of 88 mph. He unknowingly disrupts the future when he interferes with his parents lives in 1955. An alternate timeline is created in which he doesn’t exist. Dr. Emmett Brown tells him that he must now fix the timeline by convincing his parents to get together and over come the fear of the bully Biff. He manages to do so.
He now has the problem of getting back home to 1985. Dr Emmett Brown helps him do that using a bolt of lightning that strikes the clock tower. Marty gets home and finds that he has actually improved his family. Minutes later Dr. Brown Shows up in the flying time machine and informs them that he has seen the future and it is not very bright for him.
Then they go to the future 2015. Marty protects his son from getting involved in a robbery but along the way the time machine is stolen by the older Biff. He takes the time machine to 1955 and hands his younger self a copy of an almanac of all sports events from 1950 to 2000. He starts betting on all sports events and making it big. Biff creates an alternate time line in which he rules the town, kills Marty’s dad and marries Marty’s mother. The whole town becomes a sort of dystopia.