Horizon uncovers the secret world of our dreams. In a series of cutting-edge experiments and personal stories, we go in search of the science behind this most enduring mystery and ask: where do dreams come from? Do they have meaning? And ultimately, why do we dream? What the film reveals is that much of what we thought we knew no longer stands true. Dreams are not simply wild imaginings but play a significant part in all our lives as they have an impact on our memories, the ability to learn, and our mental health. Most surprisingly, we find nightmares, too, are beneficial and may even explain the survival of our species.

A wholly innovative, original, and vital history lesson, with pioneering animation, Waltz With Bashir delivers its message about the Middle East in a mesmerizing fashion. Director Ari Folman's animated quasi-documentary follows the filmmaker's emotional attempt to decipher the horrors that unfolded one night in September of 1982, when Christian militia members massacred more than 3,000 Palestinian refugees in the heart of Beirut as Israeli soldiers surrounded the area". Folman was one of those soldiers, but nearly 20 years after the fact, his memories of that night remain particularly hazy. After hearing an old friend recall a vivid nightmare in which he is pursued by 26 ferocious dogs, Folman and his friend conclude that the dream must somehow relate to that fateful mission during the first Lebanon War. When Folman realizes that his recollections regarding that period in his life seem to have somehow been wiped clean, he travels the world to interview old friends and fellow soldiers from the war. Later, as Folman's memory begins to emerge in a series of surreal images, he begins to uncover a truth about himself that will haunt him for the rest of his days.

After eight grueling years of hunting in the hot, wind-scoured desert of central Africa, an international team of researchers has uncovered one of the most sensational fossil finds in living memory: the well-preserved 7 million years old skull of a chimp-size animal, probably a male, that doesn't fit any known species. According to paleontologist Michel Brunet of the University of Poitiers in France, whose team reported the find in Nature last week, there is no way it could have been an ape of any kind. It was almost certainly a hominid — a member of a subdivision of the primate family whose only living representative is modern man.

The idea of intelligence is explored in the concepts of computers (using bits as their basic units of information), whales (in their songs and their disruptions by human activities), DNA, the human brain (the evolution of the brain stem, frontal lobes, neurons, cerebral hemispheres, and corpus callosum under the Triune Brain Model), and man-made structures for collective intelligence (cities, libraries, books, computers, and satellites). The episode ends with speculation on alien intelligence and the information conveyed on the Voyager Golden Record.