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.