Where is everyone? We have been listening for messages from outer space for more than half a century, and so far... silence, why? Are we truly alone in the universe? Or is everyone else acting like us and just doing a lot of listening? Maybe we need to be louder. Maybe we need to send more messages out there. But how do you write a letter to an extraterrestrial whose language and culture and biology and mind we have no concept of? And what do you say?
Given all of the unknowns about what they might behave, should we say anything at all?

In the third episode, the discovery of extraterrestrial life might face an impossible challenge: the physics of the universe itself; but using cutting-edge tech, experts might be on the verge of a groundbreaking find -- and the evidence could already be in hand.

The search for extraterrestrial life is an age-old quest. But recent breakthroughs make today an era like no other in the history of astronomy. From the exhilarating probing of our own solar system and the Kepler mission’s astounding discovery of thousands of extrasolar planets, to the next-generation telescopes under development, the prospects for finding life beyond Earth have never been stronger.
Still, daunting hurdles remain. How can we study anything light years away, let alone a little planet? In the vast universe, where should we even start to look? Is our failure to hear any other voices in the galaxy a sign that we are special? Join leading explorers now searching the galaxy for life and intelligence on other planets—and asks, if we do find other life in the universe... what would that mean?

Minerva B is a small rocky planet just like earth, where spacecraft Artemis has found water, organic molecules, and complex creatures. Is there something more to find?
'I am the mind of the spaceship, alone among the stars. 50 years ago, from a planet far away, the planet you call home, I launched. A journey of 28 trillion miles across the yawning time of space to the exoplanet, Minerva B: a small, rocky planet, much like Earth, but orbiting another sun. Here, I have found water, organic molecules, and microorganisms. When the news of my discovery reaches Earth years from now, some of you will be amazed. But others will remain unsatisfied, and you will ask, have I not found animals or birds? Have I not met intelligent life like us? And so, my search continues. I will find life of marvellous complexity, and the traces of a devastating loss.'

We are living in a new golden age of exploration. Planet hunters are searching far beyond our solar system and they are actually finding new worlds orbiting other suns. Thousands of these alien worlds have already been found, but this is the story of perhaps the greatest discovery yet, a star 40 light-years away with seven Earth-sized planets: Trappist-1.
This new discovery of seven alien Earth-like planets in a faraway solar system is a major milestone in our hunt for extraterrestrial life, and experts investigate the secrets of Trappist -1's mysterious worlds to reveal if we're truly alone in the universe.

Quinto sets out to discover whether aliens exist and what evidence we have to prove it. He meets with several who say they have encountered extra-terrestrial life–a man who has been abducted by aliens several times since childhood; a man who claims to have extracted an alien implant; and a woman who shows Zachary what it feels like to be abducted into a spacecraft.
Zachary also meets with the world's leading scientists at SETI in Green Banks, West Virginia. There, utilizing the world's largest telescope, they show him the methods they employ to communicate with potential other-worldly visitors and what this research has taught them about a mysterious radio signal they picked up 3 billion light years away.