恶第四季剧情介绍：
1. Boko Haram & Unnatural Selection: The Nigerian government is determined to drive militants from a terrorist group out of the country ; A new gene-editing method allow scientists to change the genetic traits of plants and animals.
2. Escape to Europe; Cycle of Terror: Following the refugee trail from the Syrian border to Europe; The global reaction to the terrorist attack in Paris impacts the fight against terrorism.
3. Right to Die: Exploring the moral, political and personal questions raised by euthanasia.
4. Beating Blindness & White Collar Weed: Doctors and researchers make incredible strides in the fight against blindness; Struggling small-scale marijuana farmers face corporate takeovers as the end of the pot-prohibition nears
5. Meathooked & End of Water: Examining the environmental harm of industrial meat operations; Assessing the depths of the world's water crisis.
6. Return to Yemen & Church and States: Examining the conflict in Yemen; Exploring the ongoing battle for LGBT equal rights in the United States.
7. Palestine Now and Viva Cuba Libre: Exploring the lives of young Palestinians today; Examining the political thawing of relationships between Cuba and the United States.
8. Afghan Women's Rights & Floating Armories: Violence and oppression are still a fact of life for women in Afghanistan; Private military contractors protect global commerce.
9. The Future of Energy: Examining the future of how to make and use energy and how to meet the growing demand as carbon emissions are cut.
10. Trump in Dubai & China in Africa: The plight of migrant workers in Dubai; Examining the increasingly prominent business relationship between China and Africa.
11. The Deal & City of Lost Children: Exploring the recent Iran deal from both sides; Tribes of homeless children live along the tracks in Kolkata, India.
12. The End of Polio and Collateral Damage: Health workers put their lives on the line in Pakistan to eradicate polio; Examining the devastating effects of unexploded ordnance in Myanmar and Laos.
13. State of Surveillance: Shane travels to Moscow to meet with Edward Snowden and discuss government surveillance programs.
14. Heroin Crisis & New Age of Nukes: The effects of America's Heroin epidemic and the next nuclear arms race.
15. Flint Water Crisis & Libya on the Brink: Examining the effects of the water crisis in Flint, Mich.; In Libya, rival militias fight to save the country.
16. Die Trying: Patients and top researchers across the U.S. discuss recent measures taken to tackle ALS; Exploring the regulatory hurdles faced by ALS patients and drugmakers.
17. Student Debt & Fecal Medicine: The correlation between student-loan borrowing and the soaring cost of college tuition; A medical revolution involves using stool from a healthy person to treat severe intestinal infections in others.
18. The New $pace Race & Closing Gitmo: NASA and a growing community of private companies decide to prepare for Mars exploration; Ex-detainees reveal what really happens behind the walls of the American prison at Guantanamo Bay, Cuba.