Software update didn't finish and now my laptop won't turn on

I ran a software update and after it finished downloading, instead of installing and restarting it just shut down. Now it won't turn on. The light comes on then flashes quickly for a few seconds, I can hear the drive click and then it shuts off. I don't think I can do anything about it but I'd like some input on what May have happened. I'm running Mountain Lion, but not sure which update.