I loved this movie. It is a timely piece about grief.
This is the story of CJ, a genius black high school student, and Sebastian, another genius black high school student, who discover time travel. And try to use it to prevent a death. The movie is told through CJ's point of view, and she is grieving for most of it. There are plot points that seem farfetched if you expect a normal adult reaction. But the movie makes sense if you think like a 16 year whose loved ones are senselessly killed in what appears to be simple situations to fix.
This is not the movie for you if you are looking for something like Back to the Future. This is a movie if you want to see what would happen if the family of a victim had the power to go back in time. It is about love, loss, and everything we do to keep each other safe.
This movie dealt with my worst fear and it didn't lie to me by offering a false ending.
****** Spoiler Alert ******
If I was CJ, I would also keep going back until I fixed things. Not necessarily because I would make things better, but because I could not live with myself if I didn't.