We've all grown up wondering if we're alone in the universe, or if, one day, we might come face to face with an alien. This is the story of our search for extra terrestrials. Does ET really exist? We're going on a journey to find out. We'll visit alien planets in search of life. We'll dive into the oceans of distant moons. Here on Earth, we'll scan the universe for alien life. And seek out the answer to one of the greatest questions - is there life on other worlds? Or, in all the vastness of space, could it really be that we are completely and utterly alone?