There are over 20,000 wildfires in a typical year; we follow crews to a few of them. First, we see the preseason physical training and a prescribed burn, which burns the flammable underbrush before the trees themselves are flammable. But since these burns can't do the whole job, we see how firespotters pinpoint lighting-caused fires that smokejumpers then have to parachute into. In the open wilderness of Idaho, the job is relatively simple. In California, where forests are closer to civilization and the chaparral forests are much more flammable, access to the fire is easier, but fighting it is harder. And in Australia, where the forests are full of eucalyptus and tea, the flammability is compounded by the acrid smoke.