re: Harry Potter and the Cursed Child Review/discussion (SPOILERS)

I've tried to read the plot summary, but it is such a mess that I can't make it through. The plot is really stupid, because they're trying to save Cedric Diggory (who they've never met) and which saving him would make sure they were never conceived. Did they not think that through, not to mention the various other ways this could effect the continuum? Plus Harry Potter seems to follow "LOST" time travel rules, to where if you ever go back in time and do something, then it always happened that way. It's why Harry wasn't killed by Dementors in PoA.