After losing his drive to continue surfing at Nazaré, Garrett McNamara decides to return to competitive surfing at other big-wave sites. In order to compete in a tournament at California's Mavericks surf site, he must surf there regularly, something that he has done many times in the past. McNamara returns to Mavericks only to suffer a horrific injury on a wave he should have aced.

To survive Mars, our species will need to evolve how we eat, drink, and build our homes. Will we need our genes to evolve as well? Sometime in the future humans will leave Earth to colonize Mars, and in doing so will begin to adapt to life on another planet in surprising ways. Evolutionary biologist Dr. Scott Solomon foresees a series of changes to our species from the size of our hearts and heads to the pigments in our skin.

Edgar Davidson agrees to talk to investigators but tells a different story. Cathy’s sister Marilyn indicates her interest in solving the case. Tom Nugent casts doubt on Gerry Koob’s story about the night of Cathy’s disappearance. The search for the other man at Cathy’s apartment Pete McKeon may have information about Koob’s relationship.
What Cathy’s roommate Sister Russell knew about the abuse and Cathy’s relationship comes into question. 'Jane Doe' and 'Jane Roe' meet for the first time and talk about the Keough. Abbie investigates Baltimore’s investigation into the abuse reports they received. Marilyn Cesnik Radakovic recalls receiving a mysterious letter from her sister after her death.

The day of the Nazaré competition has arrived, and Garrett McNamara decides not to compete but instead support his long-time friend and teammate Andrew 'Cotty' Cotton. The competition does not go smoothly, with a major accident that has secondary effects on Cotty. After the competition, Garrett tries surfing at Nazaré again and realizes that can resume big-wave surfing. The episode concludes with retrospectives from a number of the surfers who appeared on various episodes throughout the season.

A mammoth Tsunami strikes the eastern seaboard. It would be a disaster of epic proportions. Some scientists believe this catastrophe could happen one day, but how? This episode shows the Atlantic island of La Palma has collapsed several times in mega-landslides. Another could trigger a tsunami with enough power to cross the Atlantic Ocean and decimate the US East Coast.

At the very end of East Africa's Great Rift Valley, there's a 'land that time forgot'--the rolling grasslands of the Luangwa Valley. Seemingly untouched plains teem with Africa's most iconic animals. Some are unique to this place, others are critically endangered elsewhere.
Here, prey exist in remarkable balance, each taking advantage of the secret at the heart of this Eden, the mighty Luangwa River and its dramatic annual transformation from dusty inferno to emerald paradise.