Zachary Quinto explores the unpredictable and terrifying phenomenon of sinkholes to determine just what causes them. He visits a Florida man whose brother was killed when their family home was literally swallowed whole by the Earth as well as a series of sinkholes that are forming a series of caves right below the houses of a quaint suburban neighbourhood.
Whether they be a part of some biblical prophecy or further evidence of mankind's effect on our planet, he's alarmed to discover that all the same, they can strike anywhere in the world, at any time.

Space isn't vast and empty space but a dynamic, cosmic storm. It's a storm that could kill us, but without it we wouldn't be here at all. This is a story about the weird connections, the near misses, the lucky breaks that created this amazing world. For 4.5 billion years our planet has been battered and bruised and punched and pummeled but we're still standing. It's actually the battle that's built us and this is the tale of the tape.
Ever wonder how our planet got here? It was born in a cosmic storm. The violence could have destroyed us, but instead it made us.

The sun gives us warmth and light. It is the fuel of life. Without the energy of the sun almost nothing grows, thrives or lives. But the sun was not put there for our benefit. It is not this big jolly ball of nice smiling down on us, wishing us all a good day. It is not our friend. The sun is a monster. A planet killer. And we don't see that side of the sun down here.
But eight astronauts, with over 1,000 days in space between them, can show us how being up there helped them understand the suns bright fury.

Huge asteroids have smashed into the earth, and turned it into an enveloped fire, uninhabitable to almost all life on the surface. The world will get hit again. It's just a matter of when. So, what should we do as a species? Should we just, like the dinosaurs, look up and die? The reasons the dinosaurs are extinct is they didn't have a space program. We do. We have the capability to perhaps escape the Earth.
Astronaut Chris Hadfield believes the only chance for human survival is to escape from Earth and build a space colony, but there are real barriers.

This is our home, the earth it's, it's the only place we've got. It is one strange rock because it's ours and we are here and we don't know if any other place in the universe, yet, that can support life. We're very lucky to have it as our home.
Astronauts including the legendary Peggy Whitson, who spent 665 days in space, speak about how their concepts of home have changed since their experience.

Everything that lives on land, animal or plant, depends on fresh water. Yet only part of it is within reach: Much of the planet's fresh water, is locked away, almost two-thirds of it lies frozen around the poles. Even away from the poles, much of the land's fresh water freezes each winter. The need for fresh water is as strong as ever. However, the supply is becoming increasingly unpredictable and uncertain for all manner of species. We are not alone in our need for water, but we have the ability to ensure the fresh waters of the world do flow, and we alone can determine how they are shared.