Investigation into the death of a private during routine training exercises reveals the existence of an underground fight circuit. Suspicion falls upon an unpopular Sergeant when evidence of extortion surfaces.

A group of soldiers are sitting in a garage playing cards and drinking. Private Barham is drunk but decides he wants more and takes off in an armored personnel carrier, tearing through the base like a mad man. After a high speed chase, Barham crashes the vehicle into an abandoned building. When the Red Caps arrive, they make a gruesome discovery - there is a mummified corpse hanging from the debris. SIB search the abandoned building a find Barham's electrocuted body; one of the team is nearly killed in the process. It's after this accident that things begin to fall into place. The corpse is that of Private Exxner. Exxner had gone absent without leave just before his unit was sent to Iraq. He was also a known drug user. From this, SIB discovery that Exxner was the lynch pin of a drug ring that covered the whole unit, and included many who did not return from the Gulf. It's up to the team to trawl through the evidence of cowardice, bravery, loyalty and honor to find out who killed Exxner

While boar-hunting Lance Corporal Clive Morrigan becomes prey to another hunter. Investigation into his death leads from poaching to more intimate suspects; namely, his wife, his lover, and his lover's husband.

SIB must determine whether the fall a British soldier took from a hotel balcony was accidental. Their investigation uncovers stolen army supplies and an underage prostitute-smuggling ring.

Sergeant Jo McDonagh is in Bosnia on Close Protection detail as part of an international operation to capture wanted war criminal Radan Vladic. At the remote farmhouse of Vladic's proposed arrest, only the slain remains of an advance Special Air Service (SAS) team are found, seemingly murdered in an ambush. The SAS Major at the scene is ready to call the deaths collateral damage and move out, but Jo thinks there is more than meets the eye and insists the area is preserved as a crime scene.

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

During a live-firing exercise Private Andy Walden a member of the Bedford Light Infantry is killed. Meanwhile Corporal Jo McDonagh is investigating the theft of regimental mascot ""Augustus the 14th. Shorthanded Sergeant Major Burns grudgingly reinstates her back to the rank of Sergeant and a full member of his SIB team. Lance Corporal Stowe, who made the fatal mistake, faces a charge of murder and more worryingly it looks like he was high on LSD at the time.

An exhausted Private Tracey Walters of the Royal Logistics Corps is driving an army truck full of Royal Cambria Fusiliers back from a three-day exercise. There is a commotion in the back and suddenly a car is upon them from the other direction. Sam swerves but the truck goes into the car and crushes it. SIB and the German Police arrive at the scene and it seems clear Sam fell asleep or lost concentration. Worse still, Jo finds explosive flash burns on the tarmac behind the crash site.

Willi Hartung, a German Police Sergeant is shot dead by a gunman during a failed robbery attempt - just one in a sequence of similar crimes. Meanwhile, Jo and Roper investigate the apparent suicide of Corporal Luke Gemmill the driver for Lieutenant Colonel Cosgrove CO of the Wessex Regiment. Forensics prove that Gemmill was murdered - but why was his body found in the luxury car hired from a German ex-soccer star, Kramer. When Sergeant-Major Burns learns that British guns were used in both incidents, he initiates an investigation.

Journalist Theresa Brock goes missing after following the lives of the Derbyshires on a chemical warfare exercise. Whilst a pornographic picture comes back to haunt some of the men.

Sensitive information is stolen, while Roper is under threat from an IRA informant. Roper is warned that Liam Young has leaked information to the press. Since Roper investigated Liam in Ireland, there is a real danger that Liam might contact him. With his son staying with him, Roper fears what Liam might do.

Jo goes undercover to investigate a drug dealer who is suspected of smuggling illegal drugs into the country in army transport crates.