After years of empirical observation, for the first time ever, prominent mental health professionals present their observations on camera as part of their ethical 'Duty to Warn' the public of imminent danger. Medical doctors and mental health professionals go on camera, on the record, for the record - it's an eye-opening discussion, analysis, and science-based examination of the behavior, psyche, condition, and stability of Donald Trump. Unfit also examines Trump's effect on our citizenry, culture, and institutions.

When ancient architects completed construction on the Great Pyramid at Giza, they left behind the greatest riddle of the engineering world—how did builders lift limestone blocks weighing an average of two and a half tons 480 feet up onto the top of the Pyramid? For centuries, adventurers and Egyptologists have crawled through every passageway and chamber of the Pyramid, measuring and collecting data in an attempt to determine how it was built. For the first time, a revolutionary theory argues that the answer may be inside the Pyramid. Architect Jean-Pierre Houdin and Egyptologist Bob Brier use 3-D software to unlock the secret.

The fourth episode sees host Neil deGrasse Tyson exploring our eternal quest to end hunger and honoring Nikolai Ivanovic Vavilov, pioneer of modern plant breeding, who risked his life for a discovery that would change the history of science. Vavilov's story is marked by both the tenacity and creativity and is particularly tragic. Interwoven into Vavilov's somber narrative are warnings and treatments of science and its ethical implications, especially when science itself comes under attack from political forces.

Widespread dietary changes are needed if we’re to combat the range of health problems associated with obesity and the environmental damage caused by industrial farming. Switching to a vegan diet is a potential solution, but selling the idea to the meat-eaters around the world is a tricky proposition.

This programme describes the Red Army's dramatic advance and the German's brutal resistance. Witnesses reveal how the final days of the conflict were barbarous almost beyond comprehension.

Dr. Thomas Asbridge explains how in the thirteenth century, after almost two hundred years of Holy Wars, the titanic conflict between Christianity and Islam, known to history as The Crusades, reached a decisive and shocking conclusion – a chapter that despite its drama has been virtually forgotten. He explains how, in the end, the fate of the Holy Land was decided not on the hallowed ground of Jerusalem, but in Egypt; and how the ultimate outcome of the Crusades was dictated not by Christians, but by the Mongol successors to Genghis Khan, and by a Muslim slave – a fearsome warrior whose story is now all but lost to western history.