20 Things You Somehow Missed In The Prestige
9. Blind Not Deaf
In the finished film, it is shown that Angier has retained the services of stage assistants who are blind and who remain below stage whilst he performs his Transported Man act using Tesla's machine, presumably to keep its secret from being discovered.
However, Borden does discover one of Angier's secrets when he ventures below stage during one of these performances; not the secret of the machine itself, but part of the secret behind its consequences.
The difficulty is that, even though the stage hands are blind, they are not deaf, so they would surely be able to hear a man drowning in a water tank right next to them on a nightly basis, exposing Angier and his plan...