A series of meteorites strike the Earth in a line from northern Mexico to Kazakhstan, wreaking havoc. But a greater menace soon emerges; Black Clouds start rising from six of the craters and threatening to destroy all life on Earth. The Clouds are living beings that consume protein, in the process reducing animals to skeletons and plants to empty husks. Nations mobilize against the invaders but nothing seems to work as the Black Clouds continue to grow and devastate the planet. A group of scientists located 50 meters below ground in a specially designed facility are trapped by a Cloud and work desperately to determine a way of destroying these aliens before all life on Earth is obliterated.