The third episode looks at anxiety and explores why it is so common. It talks to neuroscientists who explain the physiological and evolutionary basis of anxiety. Although it can help animals escape predators, anxiety can cause serious problems for human beings. It talks to sufferers of anxiety and examines the different types of anxiety people can feel. It also looks at how social media can cause anxiety.

The final episode of this series looks at what happens to the brain when someone uses psychedelic drugs. It looks at how psychedelic drugs may be useful in dealing with anxiety in cancer survivors and serious depression. It explores the history of psychedelics and examines early medical experimentation with the drug. It also discussed why psychedelics were banned and examines how they affect the brain.

The last episode examines the fragile interdependence that exists between forests' wide variety of residents, including bald eagles, hunting dogs and Siberian tigers.
Over half of all the world's trees, evergreen and deciduous, stand in great assemblies. For many of us, they are places of mystery and darkness. They are key to our climate, and home to countless unique species. The boreal forest contains 750 billion trees, and it stores over 40 percent of the world's carbon, making it a vital element in the fight against climate change. In the past, we have destroyed them without hesitation. Yet, forests do have an astonishing ability to recover. If we choose to give forests time and space, they could reclothe the earth with much of the rich and varied communities of animals and plants of which we have, so recently, robbed it. A future with more forests is key to the resilience of our planet.

Sam Smith's book 'The Jordan Rules' exposes the darker side of Michael Jordan's competitiveness, and questions arise about whether he has a serious gambling problem, but he remains focused on winning a new title in 1993. Dealing with the pitfalls of fame and attempting to complete the first three-peat leave Jordan increasingly exhausted and isolated.

Foo Fighters prepare to record at the Austin City Limits Studio, with blues guitarist Gary Clark, Jr. In this episode is examined the roots of Austin's music scene, with interviews featuring Billy Gibbons from ZZ Top, and Roky Erickson from 13th Floor Elevators, who is considered one of the American fathers of psychedelic rock. Dave also chats with Terry Lickona, the executive producer of Austin City Limits. The song 'What Did I Do? / God As My Witness' is recorded during this chapter.

This second instalment looks at how Vladimir Putin arrived in the Kremlin as a vulnerable and unknown president, whom the Russian oligarchs expect to control. The programme reveals how he asserted his hold on power and ultimately surrounded himself with his KGB peers, as well as his philosophy as regards traitors and enemies. The film also examines the stories of businessman Boris Berezovsky and defector Alexander Litvinenko, who both stood up to Putin and wound up dead on British soil.