Alien lifeform (something like the blob) deadly to all races ,so dangerous that it is blockaded on a planet. Somehow a ship lands and what is left of the alien escapes to Earth and crashes in the ocean, I think. Aliens send out a ship to try and find it so they can trap it again. Alien comes in contact with a human, turns out it had just been looking for a partner/host one compatible with it. The race of man is and it starts to spread and mankind improves as it links mankind together.