MI5's mainframe has been hacked into. But Tom and his team think they have found a lead in the form of an I.T. teacher, so Zoe is sent undercover to get close to him and find out his secrets. Will they be able to stop the culprit before the inner sanctum is breached and every agents' identity revealed?

After stealing a large amount of money from a bank, a man is found crucified on the moors. The Treasury call in the team to investigate, but when Harry decides to take the mission further Danny's life is put in danger.

A French scientist has gone renegade and taken a top secret weapon called Firestorm with him, which he is threatening to sell to the highest bidder. Now he has ended up in the UK, and MI5 is forced to work with French Intelligence. But the British want the technology. They have to steal the technology without the French finding out, using an agent that if caught has no affiliation to Five. But there is a burglary at Harry's flat which puts the operation in jeopardy. Or does it?