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.

As dozens of top surfers from across the world arrive in Nazaré to train and prepare for a major big-wave competition, Garret McNamara continues to struggle with his physical injuries and mental preparedness. He knows he is not ready to surf in the competition but seeing the other surfers makes him consider competing anyway. Garrett also has misgivings about the state of safety plans at the competition, and tries to convince the organizers to beef up their plans.

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.

Science may soon make the dream of traveling to Mars a reality, but how will we live once we get there? How will we manage our basic human needs of food, water, and shelter on a planet known for its barren surface conditions, high radiation levels, and toxic dirt?

As their high-profile trial begins, Willy and Sal attempt to neutralize witnesses against them in a variety of ways — some legal, others not so much.