After fifteen years of estrangement, bookish Zelda Jones reunites with her best friend from
high school, Cassie . At the start of their new relationship, it’s not apparent that their
interactions are going anywhere, but as the other main characters weave their way into the
plot, Zelda learns about time travel on a
single, static timeline, and
the pieces lock nicely into place.
Oh, and Dave’s grandfather had a plot to go back and
kill Hitler, but that’s not really relevant to Zelda (and Cassie and
Walter and John and Charlie).
— Michael Main
If you do travel back in time, even though it’s in your subjective future, it’s in
the objective past. So if you could travel back in time and if you were determined to
change the past, when it came down to it, you’d either decide not to, or you’d fail.