In the 1960s and 1970s a generation of Mexican Americans, frustrated by persistent discrimination and poverty, find a new way forward, through social action and the building of a new "Chicano" identity. The movement is ignited when farm workers in the fields of California, led by Cesar Chavez and Dolores Huerta, march on Sacramento for equal pay and humane working conditions. Through plays, poetry and film, Luis Valdez and activist Corky Gonzalez create a new appreciation of the long history of Mexicans in the South West and the Mestizo roots of Mexican Americans. In Los Angeles, Sal Castro, a schoolteacher, leads the largest high school student walkout in American history, demanding that Chicano students be given the same educational opportunities as Anglos. In Texas, activists such as Jose Angel Gutierrez, create a new political party and change the rules of the electoral game. By the end of the 1970s Chicanos activism and identity have transformed what it means to be an American. Chicano and Latino studies are incorporated into school curriculum; Latinos are included in the political process.

Soldiers and officers continually came into conflict with their consciences. How much freedom did individuals have? Were they executing Hitler's criminal plans, or was it the Wehrmacht's war? There were crimes against humanity, against civilians, prisoners of war, and there was the Holocaust itself. The Trent Park records discovered and analysed by historian Sönke Neitzel, author of Tapping Hitler's Generals, show that the 84 German generals who were interned at Trent Park were aware of the severity of the war crimes they had been involved in and that some discussed them almost compulsively. They included the Commissar Order, to kill any Soviet commissar, and Rathenau's order to kill the Jews, including children.

Since Caesar's days, Germanic warriors and Roman legionaries had often met in battle. Rome's power seemed invincible. But then, in the year 9 AD, the Germans mounted a rebellion.

In this final episode, Mary Beard delves even deeper into ordinary Roman life by going behind the closed doors of their homes. She meets an extraordinary cast of characters - drunken housewives, teenage brides, bullied children and runaway slaves - and paints a more dynamic, lusty picture of Roman family life. Mary uncovers their preserved beds, furniture and cradles, tries on Roman wedding rings and meets some eccentric wives like Glyconis, praised by her husband for liking a drink or two, and Allia Potestas, who lived in a Roman menage a trois. Mary explores Roman parenting, childbirth and children, including Sulpicius Maximus, an 11-year-old schoolboy who was worked to death by his pushy parents, and Geminia Mater, a 5-year-old tomboy. Finally, Mary paints a more nuanced picture of Roman slavery and asks why if it was such a brutal institution did many Romans choose to be buried with their servants - living cheek by jowl in death, as in life

Richard Dawkins deals with some of the philosophical and social ramifications of the theory of evolution. Dawkins starts out in Kenya, speaking with palaeontologist Richard Leakey. He then visits Christ is the Answer Ministries, Kenya's largest Pentecostal church, to interview Bishop Bonifes Adoyo. Adoyo has led the movement to press Kenya's national museum to sideline its collection of hominid bones pointing to man's evolution from ape to human.[5] The collection includes the Turkana Boy discovered by Kamoya Kimeu, a member of a team led by Richard Leakey in 1984. Dawkins discusses social darwinism and eugenics, explaining how these are not versions of natural selection, and that 'Darwin has been wrongly tainted'. He then meets with evolutionary psychologist Steven Pinker to discuss how morals can be compatible with natural selection. He goes on to explaining sexual selection, with peafowls as an example. To find out whether sexual selection plays a role for altruism and kindness among humans, he visits women who are looking for sperm donors, as well as a sperm bank manager. Dawkins also explains kin selection and selfish genes.

This episode explores the nature of the greenhouse effect (discovered by Joseph Fourier and Svante Arrhenius), and the evidence demonstrating the existence of global warming from humanity's influence. Tyson begins by describing the long-term history of the planet Venus; based on readings from the Venera series of probes to the planet, the planet had once had an ocean and an atmosphere, but due to the release of carbon dioxide from volcanic eruptions, the runaway greenhouse effect on Venus caused the surface temperatures to increase and boiled away the oceans. Tyson then notes the delicate nature of the amount of carbon dioxide in the atmosphere can influence Earth's climate due to the greenhouse effect, and that levels of carbon dioxide have been increasing since the start of the 20th century. Evidence has shown this to be from mankind's consumption of oil, coal, and gas instead of from volcanic eruptions due to the isotopic signature of the carbon dioxide. The increase in carbon dioxide has led to an increase in temperatures, in turn leading to positive feedback loops of the melting polar ice caps and dethawing of the permafrost to increase carbon dioxide levels. Tyson then notes that humans have discovered means of harvesting solar power, such as Augustin Mouchot's solar-driven motor in the 19th century, and Frank Shuman's solar-based steam generator in the 1910's. Tyson points out that in both cases, the economics and ease of using cheap coal and oil caused these inventions to be overlooked at the time. Today, solar and wind-power systems would be able to collect enough solar energy from the sun easily. Tyson then compares the motivation for switching to these cleaner forms of energy to the efforts of the Space race and emphasizes that it is not too late for humanity to correct its course.