Al Capone moves back to Chicago and takes over two floors of the city's finest hotel, the Lexington. With a thriving business and Chicago politicians in his back pocket, Capone soon reaches a level of celebrity normally reserved for athletes and entertainers. As Capone's profile grows, he begins to indulge in all that the Roaring '20s have to offer, including cocaine. While Capone enjoys his reign at the top of the Chicago underworld, Irish gangster Bugs Moran seeks to take him down as revenge for the deaths of his partners Dean O'Banion and Hymie Weiss. On March 7, 1928, Moran orders a hit on one of Capone's top associates, Jack McGurn, the man who took out Hymie Weiss. McGurn survives but Capone decides to retaliate by taking out Moran and as many of his men as possible - all at once. On February 14, 1929, Capone's men dress as law enforcement and raid the liquor buy. They order Moran's men to face the wall for handcuffing, but while their backs are turned, Capone's men shoot all of them. Firing 70 rounds of ammunition in less than 10 seconds, the assassins carry out the biggest gangland hit in American history that will come to be known as the St. Valentine's Day Massacre. Through a stroke of luck, Moran avoids the massacre, but knows he's been defeated.

In 2000, Bill and Hillary Clinton owed millions of dollars in legal debt. Since then, they’ve earned over $130 million. Where did the money come from? Most people assume that the Clintons amassed their wealth through lucrative book deals and high-six figure fees for speaking gigs. Now, Peter Schweizer shows who is really behind those enormous payments. He detailed patterns of official corruption in Washington that led to congressional resignations and new ethics laws. He follows the Clinton money trail, revealing the connection between their personal fortune, their “close personal friends,” the Clinton Foundation, foreign nations, and some of the highest ranks of government.

Chris Lintott and Maggie Aderin-Pocock report on the reaction to the dramatic announcement of the discovery of phosphine gas in the clouds of Venus, a gas that could be a sign of life. Venus remains an inhospitable and unlikely host. But if not Venus, where in the solar system is the best place to look for alien life? Chris and Maggie investigate the latest missions to Mars and the icy moons of Jupiter and Saturn. Away from the search for life, Pete Lawrencepreviews the best meteor showers of the year.

Mathematician Dr Hannah Fry explores the mystery of maths. It underpins so much of our modern world that it's hard to imagine life without its technological advances, but where exactly does maths come from? Is it invented like a language or is it something discovered and part of the fabric of the universe? It's a question that some of the most eminent mathematical minds have been wrestling with. To investigate this question, Hannah goes head first down the fastest zip wire in the world to learn more about Newton's law of gravity, she paraglides to understand where the theory of maths and its practice application collide, and she travels to infinity and beyond to discover that some infinities are bigger than others.
In this episode, Hannah goes back to the time of the ancient Greeks to find out why they were so fascinated by the connection between beautiful music and maths. The patterns our ancestors found in music are all around us, from the way a sunflower stores its seeds to the number of petals in a flower. Even the shapes of some of the smallest structures in nature, such as viruses, seem to follow the rules of maths. All strong evidence for maths being discovered. But there are those who claim maths is all in our heads and something we invented. To find out if this is true, Hannah has her brain scanned. It turns out there is a place in all our brains where we do maths, but that doesn't prove its invented.
Experiments with infants, who have never had a maths lesson in their lives, suggests we all come hardwired to do maths. Far from being a creation of the human mind, this is evidence for maths being something we discover. Then along comes the invention of zero to help make counting more convenient and the creation of imaginary numbers, and the balance is tilted in the direction of maths being something we invented. The question of whether maths is invented or discovered just got a whole lot more difficult to answer

Plants' solutions to life's challenges are as ingenious and manipulative as any animal's. Innovative time-lapse photography opens up a parallel world where plants act like fly-paper, or spring-loaded traps, to catch insects. Vines develop suckers and claws to haul themselves into the rainforest canopy. Every peculiar shape proves to have a clever purpose. The dragon's blood tree is like an upturned umbrella to capture mist and shade its roots. The seed of a Bornean tree has wings so aerodynamic they inspired the design of early gliders. The barrel-shaped desert rose is full of water. The heliconia plant even enslaves a humming bird and turns it into an addict for its nectar.

Beginning with the separation of the fuzzy thinking and pious fraud of astrology from the careful observations of astronomy, Sagan follows the development of astronomical observation. Beginning with constellations and ceremonial calendars (such as those of the Anasazi), the story moves to the debate between Earth and Sun-centered models: Ptolemy and the geocentric worldview, Copernicus' theory, the data-gathering of Tycho Brahe, and the achievements of Johannes Kepler (Kepler's laws of planetary motion and the first science-fiction novel).