A spaceship lands back on Earth after a failed mission, but the astronauts have been replaced by hideous creatures that can penetrate people's bodies and make them explode. A group of cave explorers are attacked by the monsters inside an underground cave, but the survivors are in for a surprise when they finally manage to escape the trap... A spaceship lands back on Earth after a failed mission, but the astronauts have been replaced by hideous creatures that can penetrate people's bodies and make them explode. A group of cave explorers are attacked by the monsters inside an underground cave, but the survivors are in for a surprise when they finally manage to escape the trap... Parental Guide