We are in the grip of an allergy epidemic. 50 years ago one in 30 were affected, but in Britain today it is closer to one in three. Why this should be is one of modern medicine's greatest puzzles. In search of answers, Horizon travels round the globe, from the remotest inhabited island to the polluted centres of California and the UK. We meet sufferers and the scientists who have dedicated their lives trying to answer the mystery of why we are becoming allergic to our world.

SETTING: 80 million years ago in the South American forests of Patagonia. The world is a very dangerous place for tiny hatchlings like Alpha, a female saltasaur. Follow Alpha along the road of her growth years, from before her birth through asolescence and on to adulthood, as she learns how to survive and beat the odds.

With more board configurations than there are atoms in the observable universe, the ancient Chinese game of 'Go' has long been considered a grand challenge for artificial intelligence. On March 9, 2016, the worlds of Go and AI collided in South Korea for an extraordinary best-of-five-game competition, coined the Google DeepMind Challenge Match. Hundreds of millions of people around the world watched as a legendary Go master took on an unproven AI challenger for the first time in history.
AlphaGo chronicles a journey from the halls of Cambridge, through the backstreets of Bordeaux, past the coding terminals of DeepMind in London, and, ultimately, to the seven-day tournament in Seoul. As the drama unfolds, more questions emerge: What can artificial intelligence reveal about a 3000-year-old game? What can it teach us about human mind?

The 1980s was a time when artists in both the UK and US were delivering powerful social commentary in their songs. Dylan Jones selects some of the finest alternative voices from this era. From The Cure on Top of the Pops at the beginning of the decade to The Stone Roses' debut TV performance in 1989, this episode takes a comprehensive look at the alternative music of an entire era. It also features powerful live performances from Billy Bragg, Tracy Chapman, Bronski Beat and The Selecter. In addition, there are archival gems from Pixies, The Smiths, Suzanne Vega, The Fall, REM and many more.

American exchange student Amanda Knox is convicted and eventually acquitted for the 2007 death of another student in Italy. Was she a cold-blooded psychopath who brutally murdered her roommate or a naive student abroad trapped in an endless nightmare? Directors Rod Blackhurst (Tribeca Audience Award-winner Here Alone) and Brian McGinn (IDA Award-winner Chef's Table) and producer Mette Heide (Peabody Award-winner India's Daughter) explore the notorious case that made headlines around the world.

Someone once observed: 'America is great because she is good; if she ever ceases to be good she will cease to be great.' Today that notion of the essential goodness of America is under attack, replaced by another story in which theft and plunder are seen as the defining features of American history-from the theft of Native American and Mexican lands and the exploitation of African labor to a contemporary foreign policy said to be based on stealing oil and a capitalist system that robs people of their "fair share"