C15 are pursuing a German terrorist cell who, having thrown a CIA agent off a balcony, are planning a new operation. Doyle captures a female member but Bodie, posing as an arms merchant, has his cover blown and is taken hostage by the gang to exchange with her. As the two groups meet at the air-field for the trade-off, the gang tie fifteen pounds of explosives to him.
- A CIA agent is thrown out of his hotel window in London by a German terrorist cell. His murder prompts CI5 to investigate and the trail leads to Christine Herzog (Brigitte Kahn), a German terrorist in hiding. At the point of arresting her in a public library, she makes contact with Karen (Vickery Turner) and they are separately followed by Bodie and Doyle instead. Bodie loses Karen at Wembley Park station but Doyle tracks Herzog to a canal, where she dumps some weapons. After a shoot-out, Herzog is arrested and interrogated.
Meanwhile, intelligence links Karen to Werner Dreissinger (Michael Byrne) and his terrorists. Cowley works out that the gang intend to attack a meeting of foreign ministers and the weapons dumped in the canal were meant to be recovered and used in the attack. Bodie stands in for an arms dealer supplying new weapons for the gang but is taken hostage after his cover is blown in a staged shoot-out with Doyle.
Cowley and Dreissinger arrange an exchange of hostages (Bodie for Herzog) but it is still left open whether Herzog wanted to abandon her terrorist career or was working for the gang. At the airfield where the swap takes place, Bodie manages to escape and the terrorist gang are killed by snipers. Herzog is shot by Karen and dies in Cowley's arms, whilst with his last breath Dreissinger detonates explosives that had been strapped to Bodie but were removed by Doyle and thrown away moments before the blast.