Uncrossing the Stars
Adapted from a Tumblr prompt: instead of one adult, postwar character waking up at age eleven with full knowledge of what's to come and a determination to make it go better this time around, what if several of them did?
Or: Harry, Ron, Hermione, Ginny, Draco, Neville, Luna, Fred, and George each find themselves children again, fully aware of what's to come and plotting like mad to make it not happen--and each completely unaware that their classmates have found themselves in the same situation and are planning much the same thing.
One person armed with foreknowledge can deftly reweave the timestream. Several people armed with foreknowledge are more likely to tangle it into spaghetti. And it doesn't help that maybe not everyone wants the same happy ending.
how do we turn on the light?