Danny and Fiona investigate a house they suspect is being used by North African terrorists. While the agents are installing a listening device, a gang of terrorists take them hostage.

Suspicions are aroused when a known mercenary, recently linked to a new player on the arms smuggling circuit, is seen visiting an old Soviet arms dump. MI5 pull him in for questioning.

A celebrity couple on the wane are terrified when their baby is kidnapped. They demand MI5 handle the investigation, but soon MI5 learns that there's more to this kidnap than first appears.

MI5 are alarmed when they discover a group is hacking into computer systems across the country. Ruth investigates the possibility that Islamic terrorists might be behind the threat.

Zoe is caught up in the deadly fallout of an abortive mission and must stand trial for conspiracy to murder. Can an MI5 officer be culpable for the death of an undercover police officer, killed by a member of a Turkish gun-running gang?

A scientist is rumoured to be negotiating with terrorists who want to buy his potentially deadly research. Intending to frighten him off, Danny and Zoe track him onto a North Sea ferry. But things are worse than they feared and they must take more drastic action.

The latest round of Middle East peace talks are abruptly halted when a key delegate is killed. With the peace process derailed, MI5 investigate a newspaper mogul and renowned Israeli extremist.

Danny and the team must uncover the truth behind an assassination attempt on a famous novelist. Was he the real target? And who is the enemy?

Harry reawakens sleeper agent Fred Roberts, a renowned chemist and family man. As Fred becomes more deeply involved with deadly terrorists, Tom has a crisis of conscience which could jeopardise his career.

Tom Quinn has disappeared after shooting his boss. He is also accused of assassinating the Chief of Defence Staff. The Joint Intelligence Committee Chairman opens a punitive investigation of MI5.