Cannot boot up, get folder with ? What to do?

I am using Yosemite on my iMac. When attempting to boot up the other day I had a white screen with the Apple logo and a status bar. No tone at the beginning of the process. Eventually I saw script on the upper left of the screen but it was there only a couple of seconds. The screen went black for a short period. At that point a file folder with a question mark in it began to flash on a white screen.

I turned it off and unplugged for a while. Then turned back on while holding down the option key. This gave me the choice of the Mac hard drive or recovery 10.10.3. I have tried both to no success. Status bar stop at about half way.

Anyone have any suggestions?