Who is in the cistern???

[Apjjm]

I tried really hard to see what was inside that concrete box. Someone, real or imaginary, was getting drowned though. Progress at this point was a necessity as I have mild water phobia.

If you do manage to get on top of the box, to look through the grating, it turns out there isn't anything inside: http://i.imgur.com/t6ElI.jpg

Only because you're not really supposed to be able to get up there.

True