In the second episode of this two-part series, the search continues for signs of what happened on the day the dinosaurs died. Scientists uncover extremely rare fossils and more evidence that could link the dig site in North Dakota to the asteroid that wiped out the dinosaurs 66 million years ago. Among the fossils are tiny spheres of glass locked in amber. Inside one of the spheres is a speck of rock that appears to be a chemical match to the killer asteroid itself. And scientists uncover one of the most spectacular finds of all: an almost perfectly preserved dinosaur leg. Sir David Attenborough guides us on a search for clues that could provide an unprecedented snapshot of what happened in the dinosaurs' final moments on Earth.

Thousands of ancient footprints stretch for miles across New Mexico's White Sands National Park, capturing moments when Ice Age humans encountered now-extinct beasts, including mammoths and enormous ground sloths. These footprints tell an intimate story about what life was like during the Ice Age and reveal surprising new evidence about when humans arrived in North America.