A car bomb explodes in Liverpool and Zoe is sent undercover to investigate. Tom's life gets complicated when he falls in love with a woman he met while working undercover.

One of Danny's agents, Osprey, feeds him the information that 20 bombs have gone astray in the Liverpool area. Unfortunately she can’t help with who or where they are destined for. Everything comes more clearly into focus when a car bomb explodes in a suburban street, killing a family-planning doctor and her daughter.

Tom is furious when he finds out a known pro-life extremist, Mary Kane, has been allowed to sneak into the country without being noted. He knows she’s dangerous. She’s already been sentenced to death in her absence in Florida for a major bomb attack. A bit of background work shows that the first bomb marked an important anniversary. When the team realise her beloved husband’s execution is soon to take place they know when to expect the next atrocity.

Unfortunately MI5 are not the only people on the trail of Mary Kane. The CIA want her back in the USA and they want her now. But Tom’s not so keen to hand her over. He knows that if she’s just packed back to America that leaves 19 bombs on the loose, and it’s a risk he can’t take. Mary Kane’s house is bugged and Zoe goes undercover.

Posing as a sympathiser Zoe tricks one of Mary Kane’s supporters into giving away the plan. Zoe heads undercover again. This time she is posing as the intended victim. The team lure Mary Kane right into their trap her bomb is jammed and she’s arrested. Tom persuades Mary to do a deal. She gives away her accomplices, and in return he makes sure that when she’s sent back to the USA it’s not to Florida where certain death awaits. However, Tom has the last laugh. He hands her over to the CIA and gives her a Florida tourism brochure. Looks like she’s only going back for a short visit.