The stakes are raised in season two of MI-5, as the threat to national security increases and the need to thwart the terrorists operating within the UK becomes more urgent. Tom is investigating a Serbian terrorist plot. His girlfriend and her daughter are trapped in Tom's house with a lap-top which is thought to contain a bomb. Meanwhile another bomb is primed to explode and this one kills the Secretary of State for Northern Ireland. Adding to the possible dangers faced by other government officials, Tom learns from his American colleague that an assassin is in town, the CIA know about him but they haven't told MI-5.