An abortion doctor is executed by an American pro-life terrorist; Mary Kane. An informant reveals that this is just the tip of the iceberg as Mary has 20 more bombs and plans on using them.
The team uncover connections between racist ring-leaders, politicians and mass killings of immigrants, and are forced to go undercover in order to investigate.
Ellie questions whether she can cope with dating a spy, and Zoe discovers Tessa is up to something. Meanwhile, Tom's mentor is working undercover at an anti-Bush rally when his methods start to appear dangerously unconventional.
Patrick McCann, the leader of an Irish splinter group, walks into a safe house armed with a grenade, and demands to speak to someone at MI5 about some crucial information he has on a Middle-Eastern terrorist group called Asabiyah.
