We follow Ahmed Taseer, a boy from an isolated mountain village located in Nuristan Province, Afghanistan. Before forcible conversion to Islam in the 19th Century, the region was known as Kafiristan, land of the Kafirs, the unbelievers.
The story extends over a period of about 20 years, during which Ahmed's friend Yusuf, a recent orphan to be adopted by Ahmed's family, is seized by the Taliban to become a suicide bomber. This prompts Ahmed and his friend Haziz to retaliate by locating the Taliban base and guiding a US drone that resuls in destruction of the base.
The ruling family in the village are the Durrani. They collaborate with the Taliban and form part of the Taliban's opium distribution network. Ahmed's father represents the villagers in a land dispute with the Durrani. In a separate incident Ahmed's sister is raped and beaten by a member of that clan. Ahmed's father is killed when seeking justice for his daughter. Threatened by the Durrani, Ahmed flees the village with his mother and injured sister and, under cover of darkness, crosses the border into the Kalash Valleys, a non-Muslim area of Pakistan from which his mother's family originated. During their journey to the Kalash, Ahmed's sister dies from her injuries.
After ensuring his mother's safety and security with the Kalash, Ahmed moves on to Peshawar and pays a people smuggler for a journey to Australia. He ends up in a detention centre for 18 months before being released into the community. During this process he meets and works with a group of welcoming Australians at a building site. They provide him with insights about his new country and he becomes aware that they are all refugees of one kind or another.
He is ambivalent about religion but sometimes attends the mosque where he inadvertently becomes involved with a small group of men who are planning a terrorist act on Australian soil. Simultaneously he becomes romantically involved with a fellow student at the college. With his girlfriend Emily's support, he informs the Australian Security Intelligence Organisation (ASIO) of the budding terrorist group and works with ASIO to bring the group undone.
Emily, like Ahmed, is similarly conflicted about religion and they discuss their respective doubts and, together, develop a view that puts moral values before religious rituals and beliefs. On graduation, Ahmed and Emily go their separate ways. She takes up an internship with a legal firm in Melbourne. He accepts an engineering traineeship with a large mining company and moves to Western Australia. There he meets Sima a young woman who is part of the Shia Hazara community in Perth. Like Ahmed, Sima's family departed Afghanistan as refugees.
As a spin-off from his association with ASIO, Ahmed is approached by the Australian Security Intelligence Service (ASIS) to help with tracking a terrorist group in Quetta, Pakistan. He accepts and undertakes the necessary training. Unknown to ASIS, Ahmed's decision to become involved was due primarily to his desire to "complete some unfinished business". He wished to clear the past and move on.
Ahmed travels to Quetta and, through several steps, he locates the ASIS targets and arranges their elimination. Ahmed then drops out of sight and returns to his home village and resolves his unfinished business before returning to his new life.