The film opens in Nairobi, Kenya, where Alia Mo'Allim, a young girl, twirls a hula hoop in her backyard.
British Army Colonel Katherine Powell wakes up and hears that an undercover British/Kenyan agent has been murdered by the Al-Shabaab group. From Northwood Headquarters she takes command of a mission to capture three of the ten highest-level Al-Shabaab leaders, who are meeting in a safehouse in Nairobi.
A multinational team works on the capture mission, linked together by video and voice systems. Aerial surveillance is provided by a USAF MQ-9 Reaper drone controlled from Creech Air Force Base in Nevada by Second Lieutenant Steve Watts. Undercover Kenyan field agents, including Jama Farah, use short-range ornithopter and insectothopter cameras to link in ground intelligence. Kenyan special forces are positioned nearby to make the arrest. Facial recognition to identify human targets is done at Joint Intelligence Center Pacific at Pearl Harbor in Hawaii. The mission is supervised in the United Kingdom by a COBRA meeting that includes British Lieutenant General Frank Benson, two full government ministers and a ministerial under-secretary.
Farah discovers that the three high-level targets are now arming two suicide bombers for what is presumed to be an attack on a civilian target. Powell decides that the imminent bombing changes the mission objective from "capture" to "kill". She requests Watts to prepare a precision Hellfire missile attack on the building, and solicits the opinion of her British Army legal counsel. To her frustration, her counsel advises her to seek approval from superiors. Benson asks permission from the COBRA members, who fail to reach a decision and refer the question up to the UK Foreign Secretary, presently on a trade mission to Singapore. He does not offer a definite answer and defers to the United States Secretary of State, who immediately declares the American suicide bomber an enemy of the state. The Foreign Secretary then insists that COBRA take due diligence to minimise collateral damage.
Alia, who lives next door, is now near the target building selling her mother's bread. The senior military personnel stress the risk of letting would-be suicide bombers leave the house. The lawyers and politicians involved in the chain of command argue the personal, political and legal merits of and justification for launching a Hellfire missile attack in a friendly country not at war with the US or UK, with the significant risk of collateral damage. Watts can see the more direct risk of little Alia selling bread outside the targeted building, and they seek to delay firing the missile until she moves.
Farah is directed to try and buy all of Alia's bread so she will leave, but after paying her his cover is blown and he is forced to flee without collecting it. Seeking authorisation to execute the strike, Powell orders her risk-assessment officer to find parameters that will let him quote a lower 45% risk of civilian deaths. He re-evaluates the strike point and assesses the probability of Alia's death at 45–65%. She makes him confirm only the lower figure, and then reports this up the chain of command. The strike is authorised, and Watts fires a missile. The explosion destroys the building and injures Alia, but one conspirator survives. Watts is ordered to fire a second missile, which strikes the site just as Alia's parents reach her. They rush Alia to a hospital, where she dies.
In the London situation room, the under-secretary berates Benson for killing from the safety of his chair. Benson counters that he has been on the ground at five suicide bombings and adds as he's leaving, provoking her to tears: "Never tell a soldier that he does not know the cost of war."
United Kingdom
Helen Mirren as Colonel Katherine Powell, a UK military intelligence officer
Alan Rickman as Lieutenant General Frank Benson, Deputy Chief of the Defence Staff
John Heffernan as Major Howard Webb, Army Legal Services Branch
Babou Ceesay as Sergeant Mushtaq Saddiq, Risk Assessment Officer
Carl Beukes as Sergeant Mike Gleeson
Jeremy Northam as Brian Woodale MP, the Minister of State for Foreign Affairs
Iain Glen as James Willett MP, the Foreign Secretary
Monica Dolan as Angela Northman MP, the Parliamentary Under-Secretary of State for Africa
Richard McCabe as Attorney General George Matherson
United States
Aaron Paul as 2nd Lieutenant Steve Watts, a USAF MQ-9 pilot
Phoebe Fox as A1C Carrie Gershon, USAF
Lemogang Tsipa as SrA Matt Levery, USAF
Kim Engelbrecht as A1C Lucy Galvez, USAF
Gavin Hood as Lieutenant Colonel Ed Walsh, USAF
Michael O'Keefe as US Secretary of State Ken Stanitzke
Laila Robins as Jillian Goldman, US National Security Council Senior Legal Advisor
Kenya
Vusi Kunene as Major Moses Owiti, leader of the Kenyan Army Special Forces
Barkhad Abdi as Jama Farah, an undercover Kenyan NIS agent
Warren Masemola as Atieno, a Kenyan NIS agent
Ebby Weyime as Damisi, a Kenyan NIS surveillance agent
Armaan Haggio as Musa Mo'Allim
Aisha Takow as Alia Mo'Allim
Vusi Kunene, South African
Warren Masimula, South African