As we know, in the end of the Fate/Zero, Emiya Kiritsugu refused the Holy Grail, but why?
I remember that the Holy Grail can make any dream come true, but the way is needed. And Kiritsugu's way to achieve the dream that saving all the human is killing a great portion of human?
Also, I have heard the Holy Grail had been polluted. So the way to achieve Kiritsugu's dream may be killing all the human? But what or who polluted the Holy Grail? And how did Kiritsugu realise that the Holy Grail was polluted?
And why did Kiritsugu's wife and daughter appear in the end of Fate/Zero?