The documentary deals with the future of conservation. It begins by looking at previous efforts. The 'Save The Whales' campaign, which started in the 1960s, is seen to have had a limited effect, as whaling continues and fish stocks also decline. In the 1990s, as head of the Kenya Wildlife Service, Richard Leakey took on the poachers by employing armed units. Although it was successful in saving elephants, the policy was detrimental to the Maasai people, who were forced from their land. The need for "fortress" areas is questioned, and the recently highlighted Raja Ampat coral reef in Indonesia is an example. The more tourism it generates, the greater the potential for damage — and inevitable coastal construction. Sustainable development is viewed as controversial, and one contributor perceives it to currently be a "contradiction in terms". Trophy hunting is also contentious. Those that support it argue that it generates wealth for local economies, while its opponents point to the reducing numbers of species such as the markhor. Ecotourism is shown to be beneficial, as it is in the interests of its providers to protect their environments. However, in some areas, such as the Borneo rainforests, the great diversity of species is being replaced by monocultures. The role of both religion and the media in conservation is argued to be extremely important. Contributors to the programme admit a degree of worry about the future, but also optimism.

Garrett McNamara recovers from the injuries he sustained at Mavericks and begins training to return to Nazaré for another season. While surfing at Indonesia's G-Land site, Garrett suffers more injuries that threaten to take him off the waves permanently. Meanwhile, a friend of Garretts catches an 80-foot wave at Nazaré, taking the world record from McNamara. McNamara resolves to continue his hunt for a 100-foot wave.

The filmmakers challenge former Indonesian death-squad leaders to reenact their mass-killings in whichever cinematic genres they wish, including classic Hollywood crime scenarios and lavish musical numbers. Anwar Congo and his friends have been dancing their way through musical numbers, twisting arms in film noir gangster scenes, and galloping across prairies as yodeling cowboys. Their foray into filmmaking is being celebrated in the media and debated on television, even though Anwar Congo and his friends are mass murderers.
Medan, Indonesia. When the government of Indonesia was overthrown by the military in 1965, Anwar and his friends were promoted from small-time gangsters who sold movie theatre tickets on the black market to death squad leaders. They helped the army kill more than one million alleged communists, ethnic Chinese, and intellectuals in less than a year. As the executioner for the most notorious death squad in his city, Anwar himself killed hundreds of people with his own hands.
The Act of Killing is about killers who have won, and the sort of society they have built. Unlike ageing Nazis or Rwandan génocidaires, Anwar and his friends have not been forced by history to admit they participated in crimes against humanity. Instead, they have written their own triumphant history, becoming role models for millions of young paramilitaries. The Act of Killing is a journey into the memories and imaginations of the perpetrators, offering insight into the minds of mass killers. And The Act of Killing is a nightmarish vision of a frighteningly banal culture of impunity in which killers can joke about crimes against humanity on television chat shows, and celebrate moral disaster with the ease and grace of a soft shoe dance number.