Lance Corporal Paul Engels is killed by a stray mortar, and Sgt. Charlie Fleckner narrowly escapes, SIB are called in to investigate what appears to be a tragic accident. But it soon becomes clear that there are just too many suspicions to write off Engel's death - suspicions that are compounded when Engel's brother claims Fleckner's innocence might not be that clear cut. The team's investigations lead them to some photographs that indicate Engles and Fleckner shared a secret - they were involved in an apparent war crime in Iraq. More than enough motive for murder. However, the situation soon escalates when the team uncovers evidence of an illicit love affair that involves blackmail, betrayal and retribution. An affair is ultimately the cause of Engels' demise. Overshadowing the whole investigation is the increasing unrest within the team. Jo and Roper's relationship becomes more intense. Burns cannot decide if he should leave SIB and accept a commission, and Vicary's given the opportu

• Chris O'Dowd
• Douglas Hodge
• Pip Torrens