A fifth of the land on our planet is covered by desert. Deserts may appear to be barren and empty, but they are of crucial importance to life. For those that can overcome their challenges they provide a vital refuge. The Grasslands are one of our planet's most productive landscapes. They support the greatest aggregations of large animals on Earth. Cameras follow desert elephants seeking sustenance, bison roaming North American grasslands and caterpillars living the good life underground.

It's Valentine's Day and Maddi steps out on her first ever date with a romantic man. Kelvin works with a relationship specialist and puts his dating skills to the test. Michael is overwhelmed when he meets the woman of his dreams.

Olivia meets someone who seems to truly get her. Andrew has found out about a speed dating event being held in town. He works on his jokes and James Bond impersonations before going to the dinner. Jimmy and Sharnae go on a special holiday together where Jimmy plans a romantic surprise.

To help Andrew in his search for love, relationship specialist Jodi Rodgers has come to work with him - on his dating skills. Olivia hasn't given up in her search for love. Today, she's on her way to meet someone new. She's meeting Jackson. Jackson likes origami and the smell of perfume. He hates the sound of nails on a blackboard and people slurping their tea. Jimmy and Sharnae are arriving at the Gold Coast for their first-ever holiday together. And Jimmy has a surprise in store for tomorrow.

What sort of alien civilizations might exist in the vastness of space? Terra is the fictional world imagined in Episode 4, a planet nine billion years old, twice as old as Earth. Old enough that a truly advanced intelligence could evolve. It was once a fertile world, now it is barren. But life can still thrive here in artificial domes. Over time, they've evolved not to need their bodies. They exist only as neural tissue. They never age, they never die. They're monitored and maintained by robots.
If alien civilizations are statistically so likely, why haven't astronomers found any sign of them? Where is everyone? Every time we look at an individual star, that's like dropping a bucket in the ocean. We're going to have to look at a lot of stars and to search through a lot of data until we find the clue that leads us to another civilization.

On the second part of his journey through the dark ages Richard Rudgley continues into the age of the wandering peoples, the Volkerwanderung. These Northern people enjoyed a golden age unaffected by Rome and just 30 years after the Romans relinquished Britain, the 'Anglo-Saxons' made their move. The bedraggled legions are in retreat. Walls are pulled down. Mosaics shattered. And yet there never was a people called Anglo-Saxon. We look at the lasting influence of Saxon leaders like Alfred the Great, and his blue print for social justice.