There's a trope in time travel stories where the viewpoint character jumps back into to their own body, changes the past, and then returns to their body in present day. They only retain memories of the original timeline, but the world around around them has changed. I've seen it in X-Men: Days of Future Past, Hot Tub Time Machine, and Project Almanac. The thing that annoys me is how their friends respond to their return.
Example timeline (story protagonist's perspective):
|α timeline||year 2000||Bob α (age 20)||Bob's best friend Alice gets killed|
|α timeline||year 2001||Bob α (age 21)||Bob becomes a scientist and start work on a time machine|
|α timeline||year 2011||Bob α (age 31)||Bob leaps back in time|
|ß timeline||year 2000||Bob α (age 31) MIND in Bob ß (age 20) BODY||Bob saves the world, and leaps home|
|ß timeline||year 2011||Bob α (age 31)||Bob finds that (with no memories of these changes) he's a millionaire now, married to Alice!|
Alice finally gets to thank Bob for saving her life.
Thus the movie ends happily. But it never rings true for me. What if we think about what Alice has experianced? This should be simpler, as she never travels in time.
Example timeline (friend's perspective):
|ß timeline||year 2000||Alice β (age 20), Bob α (age 31) MIND in Bob β (age 20) BODY||Alice β sees Bob save the world|
|ß timeline||year 2001||Alice β (age 21), Bob β (age 21)||Bob β has no memory of saving the world|
|ß timeline||year 2002||Alice β (age 22), Bob β (age 22)||Alice β falls in love with, and marries Bob β. They set up a company together.|
|ß timeline||year 2009||Alice β (age 29), Bob β (age 29)||Alice β and Bob β company is doing so well they become millionaires|
|ß timeline||year 2010||Alice β (age 31), Bob α (age 31)||Bob α returns to “his body” replacing Bob β.|
The question is would Alice β be glad to see Bob α or devastated at the loss of her husband and business partner?