First, read the other reviews that rate this lowest - no need to repeat what they say, yes, this is a total piece of garbage. Banderas is awful, the script is pathetic, everyone involved should be ashamed. But in case you are wondering how it ends (yes, I actually watched it all, I was curious) - the letters were written by a cross-dressing physicist (I'm not kidding), the cops turn out to be the villains (Oh No!), Banderas manages to kill all three of them (shocker!), the Big Bang experiment just blows up and leaves a huge crater (whew!), Banderas gets away with the two girls and the diamonds, which they find in the gecko's tank. So now you don't need to waste your time watching to the end, stop wherever you are, it does NOT get better.
Review of The Big Bang
