Can love change the world? Morgan Freeman is on a global quest to understand how this primal force binds us together as a species. From orphanages to battlefields, from arranged marriages to life on the streets, Freeman sees how love can be found in unexpected places and how this force inspires us all.

In the last episode of the series, Freeman examines different faiths' views on miracles, meeting a man who survived falling 47 storeys and a cancer patient who believes his illness can be cured by prayer.

Can we find a way to distribute power so that everyone has their say? A U.S. president explains the challenges of making decisions that affect hundreds of millions of lives, and Freeman learns about an African woman who has created a society without men. He explores how the rise of the internet may fundamentally change how democracy works.

The pirates of the Caribbean's humble base in Nassau turns into a boomtown run by Benjamin Hornigold. But Hornigold's crew deposes him for his refusal to attack English ships; but one man, Edward Thatch, remains loyal. Meanwhile, pirate raids on British slaves provokes outrage.

The five directors, John Ford, William Wyler, John Huston, Frank Capra, and George Stevens, return to Hollywood after the war but are forever haunted by what they saw. Ford goes on a drinking bender after filming the carnage at D-Day. Stevens is wholly unprepared for the horrors of Dachau and realizes he is not there to film propaganda but to capture evidence of crimes against humanity. Wyler, who lost his hearing during the war, fears his career is over. Huston chronicles soldiers suffering from postraumatic stress disorder in the film Let There Be Light, only to have it suppressed by the U.S. government.

The fifth programme explores the alliances formed between the animal and plant worlds. Attenborough dives into Australia's Great Barrier Reef and contrasts the nocturnal feeding of coral, on microscopic creatures, with its daytime diet of algae. Some acacias are protected by ants, which will defend their refuge from any predator. Besides accommodation, the guards are rewarded with nectar and, from certain species, protein for their larvae as well. Fungi feed on plants but can also provide essential nutriment to saplings (Mycorrhiza). The connection is never broken throughout a tree's life and a quarter of the sugars and starches produced in its leaves is channelled back to its fungal partners. Meanwhile, fungi that feed on dead wood leave a hollow trunk, which also benefits the tree. Orchids enjoy a similar affiliation. Lichens are the product of a relationship between fungi and a photosynthetic associate, usually algae. They are extremely slow-growing, and a graveyard is the perfect location to discover their exact longevity. Mistletoe is a hemiparasite that obtains its moisture from a host tree, while using own leaves to manufacture food. Its seeds are deposited on another by the mistletoe tyrannulet, following digestion of the fruit. The dodder (Cuscuta) is also parasitic, generally favouring nettles, and siphons its nourishment through periodic 'plugs' along its stem. The rafflesia has no stem or leaves and only emerges from its host in order to bloom — and it produces the largest single flower: one metre across.