A science experiment while searching for the cure to mortality goes terribly wrong - the reactor explodes, sending you back in time 30 seconds.
It's just you and the six bullets in your gun against a horde of raging zombies as you attempt to prevent the explosion. Every time you fail, you're sent back again -
but this time you have your past selves to help you. Find your way through the laboratory to the reactor core and deactivate it. But hurry - time's running out.