In the last episode, Iain discovers the remarkable impact of just one plant: grass. On the savannah of South Africa he sees how grass unleashed a firestorm to fight its greatest enemy, the forests. He shows how cutting your finger on a blade of grass shows us how it transformed life in the oceans. In Senegal, he meets the cleverest chimps in the world. And, in the ruins of the oldest temple on Earth, he tells the extraordinary story of how grass triggered human civilisation.

In the last episode, in the years after Steven and Brendan's very public trials, the various members of the Avery family struggle to mend their broken lives.

At first glance, Matthew Vandyke —a shy Baltimore native with a sheltered upbringing and a tormenting Obsessive-Compulsive Disorder diagnosis— is the last person you’d imagine on the front lines of the 2011 Libyan revolution. But after finishing grad school and escaping the U.S. for 'a crash course in manhood,' a winding path leads him just there. Motorcycling across North Africa and the Middle East and spending time as an embedded journalist in Iraq, Matthew lands in Libya, forming an unexpected kinship with a group of young men who transform his life. Matthew joins his friends in the rebel army against Gaddafi, taking up arms (and a camera). Along the way, he is captured and held in solitary confinement for six terrifying months.

In the ninth episode, Steven's trial is over, but a new one is just beginning. Will the jury find the suspect's confession or his conflicting statements more believable?

In the eighth episode, after two long days of closing arguments, the jury deliberates. Steven's fate hinges on whether the jury believes police misconduct may have occurred.

A team of Australian and Chinese scientists discover mysterious ancient human remains from a remote cave in South West China. The bones are unlike any living human or any ancient human known to science, yet they were alive at the same time as humans of our own kind. Could they represent a new human species? And if so, what happened to these people?