Omg such a brilliant film!!! It reminds me of Vanishing time, but of course way more different. Some of you might get confused but thats why you have to focus and stick around the whole film. So the story was Seo-yeon the main character will get to talk to Young sook in the past. Since her year was 2019 Young sook is in 1999 so they are 20 years apart but they live in the same house. So long to short story what will happen is that seo yeon will ask a favour to young sook to save her dad in the fire accident in 1999 so when your past is changed the future will be changed as well, since young sook saved her dad now in seo yeon's present time her dad came back to life and because of that she helped young sook with her stepmother as well, until things didnt go right young sook unfortunately killed her stepmom, now that the police will be after her she asks help to seo yeon in the future.