The Prestige/WMG

Lord Caldlow survived.
Or at least. The two tricks that had much focus in the film, apart from the transporting man, were the catch-the-bullet trick and escaping from a tank of water. Considering that earlier in the film, Angier said, might it be possible that perhaps one night, even offstage or before the occurrences, he simply got... careless Explanation of how this could work:
 * The tank was locked from the outside.
 * It's still possible that one night Angier forgot to lock it. It only had to happen once out of a hundred-show run.
 * It's a trick tank; they show you the panel. The only difference is that a pick-guarded padlock is used instead of the show padlock.
 * Alternatively and relating to the below as well, Perhaps after killing the first clone, Angier realized that because of the risks, he should have a double, so he kept one, and just one, alive. And when Borden/Fallon killed Angier, that last Angier just... let it go, because he was done.
 * Though if he was willing to trust a double, one wonders why they didn't simply perform the trick as Borden did using duplicates instead of twins.

Owens (Lord Caldlow's manservant) is Angier.
Look at how Owens looks. Look at how Angier looks. Now think back to the first  Angier might have anticipated Fallon's response to   imprisonment and

Nicola Tesla is a Technocrat and a Magnificent Bastard
He planned the entire thing out to get rid of two pesky reality deviants.

Both the movie and novel take place in Assassin's Creed.
Tesla made the  based on what he learned from the POE he had for a while.

Borden or Fallon is a
What if Borden wasn't lying when he told Angier that the secret was in Tesla? It's possible that Borden had gone to Tesla to get his help, but when he realized that Tesla's machine  and could do a brilliant magic trick anyways.
 * Tesla also never denied making a machine for Borden, he could have made a machine and Borden could have found out how it worked without Tesla knowing, explaining why Tesla and his assistant didn't know exactly how the machine functioned.
 * It took me looking this page's history to make sure that I hadn't made this entry. I'm convinced this is true. It also adds new subtext to Borden's line:

Borden's wife knew about the twin
Sarah told Olivia she needed to share something about Borden before killing herself, but Olivia never met with her to learn what it was. Sarah had deduced she was living with two men (which wouldn't be too hard, if she paid attention to small clues), and she wanted to let Olivia in on the secret before it tore her apart, too. Sarah hung herself not because her marraige had fallen apart, or because her husband had a mistress, but because she realized the man she loved had been playing an extremely cruel trick on her, with no end in sight.