Reese Witherspoon explains the world of female Macaques, who use sexually ways to ensure their baby monkeys will grow up with strong male protectors. These females have helped to shape one of the most caring primate societies on earth.

One extraordinary family of fish has achieved the ultimate form of gender equality. When it comes to breeding, seahorses do it like no other animal on the planet. Their fierce females refuse to be left holding the baby. So it's the males that carry their brood. In this episode we explore the world of mating seahorses which are the only animals in the world that have a major gender role reversal.

Rehearsals briefly resume amid uncertainty over the band's future. Following a productive meeting with Harrison, the Beatles agree to abandon the idea of a live show and relocate to their Apple Corps studio to formally record the new album. Billy Preston, a musician the group met in Hamburg, joins in on the sessions on electric piano.

The Beatles continue recording as the deadline for completing the project, caused by Ringo Starr's filming schedule for The Magic Christian, approaches. McCartney continues to hope that the band will perform live for an audience and Lennon meets American businessman Allen Klein for the first time. On the penultimate day, the Beatles perform an unannounced concert on the roof of the Apple Corps building, attracting crowds of passers-by as well as the attention of the Metropolitan Police.

Will Smith confronts his fear of nature on powerful white-water rapids in Iceland. "Over five expeditions, I've followed explorers into situations that were straight-up scary. It was worth it to discover the Earth's wonders. But your boy was tripping more than once. Because when I see wilderness, you know, nothing but nature, I get nervous because I don't understand it."

In the aftermath of Japan’s devastating attack on the US Pacific fleet at Pearl Harbor, the Japanese Imperial Navy moves in for a knockout blow. A surprise attack against the island of Midway is planned to draw the remaining American aircraft carriers out for a decisive battle. Admiral Yamamoto devises a meticulous plan. But the attack is in the hands of his by-the-book Admiral, Nogumo. When a genius American code-breaker unearths their plans – the Japanese attack is thrown into chaos.