Sean O'Connor and Declan Murphy, two IRA terrorists released as part of the Good Friday Agreement, have been loaned to an al-Qa'eda training camp in Afghanistan in return for drugs, weapons and money. News of the Irishmen's mission is leaked to two former SAS soldiers, Piers Walker and Barry Ferguson. The Britons are bent on avenging the murder of a young soldier in their charge in South Armagh and see lawless Afghanistan as the perfect place for retribution. But Ferguson has a secret. Their vendetta, always against the odds, converges with the IRA men and the Islamists the day before 9/11.