What if you're still stuck on the other side of the bridge

Only three minutes have passed.So far, so good.Now comes the hard part.The professor and the janitor take the lantern and cross together.This takes them ten minutes since the janitor has to slow down for the old professor who keeps muttering that he probably shouldn't have given the zombies night vision.By the time they're across,there are only four minutes left,and you're still stuck on the wrong side of the bridge.