Black Screen on Mountain Lion Reboot

This is a MacBook Pro with the i7 in it. I downloaded Mountain Lion to run the upgrade. Went to install it and it thought for a few minutes. Then it told me it needed to reboot. It did and the screen went black. No message, no nothing. The machine was still on, though, because the chasis was warm and the I could hear the fan humming. So I held down the power button to shut it off and then turn it back on. The power light on the front of the unit comes on for a second like it's going to boot, but then it goes off and doesn't power on. So now I can't even boot my machine. Can somebody tell me what's going on here, and what I need to do to fix it?