| This trick works quite well under some circumstances, generally when you have a ton of random things going on in the campaign that you just threw in because it seemed like a good idea at the time.
Tell your players that there's been some kind of conspiracy going on in the background that has driven a lot of the game and ask them what they believe it is.
Whatever they say is true. Just act surprised at how clever they are for guessing exactly what's going on.
This little DM dodge has saved me more often than just about any other trick. In my opinion it's not a retcon if none of the players remember it. | 
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