In the movie "War of the Worlds," the aliens, referred to as Martians, are killed by earth-bound microorganisms. The Martians lack of experience with life on Earth meant that they were unable to develop immunity to infections that would be harmless to humans, or at worst easily treated. Despite their vast technological superiority over humankind, the Martians were vulnerable and could be killed. The eventual fate of the Martians was foreshadowed in the books first line, which states that they are as mortal as man.