Joe Connor (Hugh Dancy), charismatic and idealistic, is a young man taking a year out. While his friends are backpacking around India or lying on a beach in Thailand, Joe has chosen a "real" experience - teaching in a Rwandan school. He is looking forward to stunning his mates with tales of adventure and life at the sharp end. His enthusiasm for Africa makes him popular with the pupils. To Francois, the school groundsman, Joe is a real friend.

The school is headed by Father Christopher (John Hurt) an English Roman Catholic priest. Christopher has spent nearly all his working life in Africa. The cycles of violence that he has witnessed over the years, throughout the continent, have made the struggle to keep his faith alive increasingly hard. Now he is wearier than ever, fearing for Rwanda as it sinks deeper and deeper into a mire of ethnic hatred and political corruption.

Every evening Joe is on the running track coaching Marie (Claire-Hope Ashitey), a young Tutsi girl. She is an exceptional talent and Joe sees her as a shining example of a brighter future. But in the Rwanda of April 1994 ethnic tension between Tutsis and Hutus erupts into genocide. Joe's world is turned upside down.

The killing escalates through the city and the school becomes a refuge for Europeans and Tutsis. A contingent of Belgian UN soldiers, led by Capitaine Delon (Dominique Horwitz), has been stationed there to monitor the fragile peace accord but, now, as the extremist Hutu government vows to eliminate all Tutsis, the refugees wonder if the UN will really protect them from the machete-wielding Hutu militias who slowly start to surround the school.

Joe burns with a desire to "do" something, which puts him at odds with Christopher, who has become more and more hardened - Africa, he believes, is beyond hope. Joe promises a distraught Marie that she will be safe - that he will make sure the world outside doesn't desert them. He ventures out into Kigali to pick up a television crew to bring back and publicise their plight. But things turn ugly at a roadblock. Joe and the crew are held at gunpoint by drunken militia and he discovers, to his horror, that one of the thugs is Francois, his friend, with a blood-stained machete in his hand.

The killing gets closer and closer to the school but with a weak UN mandate Capitaine Delon can do nothing to stop it. The European refugees are evacuated by French troops. The Rwandans are left behind, their hope draining away. Their worst fears are realised when the UN troops are ordered to pull out and abandon the Rwandans: Joe is told he must leave too - or face certain death. Terrified, he clambers aboard a UN truck, aware that he has betrayed his promise to Marie. Joe waits on the UN truck for Christopher but is astonished to discover that he has decided to remain behind with the Rwandans - a people he has grown to love.

After the UN convoy pulls away Christopher makes one final desperate attempt to save the handful of children he can squeeze into the back of the last vehicle remaining. Marie's father Roland pushes her forward - her face is numb with fear and confusion for she knows she will never see her father again. But the truck is stopped at a Hutu roadblock. Machetes glint in the firelight and whilst Christopher tries to distract the soldiers, Marie slips silently out of the truck and starts to run, faster and faster, deeper and deeper into the African bush...