Incendiary is the story of a group of terrorists who bomb a football match going on in London. Two of the victims were a boy (Sidney Johnston) and his father. His mother (Michelle Williams) was in the act of being unfaithful to her husband Lenny (Nicholas Gleaves) with a reporter named Jasper (Ewan McGregor) while the event unfolded. After learning of what happened to her son, guilt overruns her conscious, and she sets out to find out who is responsible for her son's death. The mother meets the son of one of the terrorists with help from Jasper and tries to befriend him to learn why his father did what he did, but soon learns he had no idea his father was responsible for the incident. To further complicate matters, Lenny's boss, Terrence Butcher (Matthew Macfayden) shows interest in the mother, and later explains to her that he had prior knowledge of the attack taking place.