An engineering firm is hijacked by armed men, who shoot a security guard before driving off. The police give chase, but Detective Inspector Regan and Detective Sergeant Carter are forced to hide behind their own vehicle as the gang opens fire and disappears over a wall.

Carter meets his informant Albert Milligan, who tells him that a man named Tober is responsible. Back in the office, Regan and Carter discover that he's an ex-Marine with a violent reputation and that he's wanted for court-martial.

In the gang's hideout, Tober complains that he's being asked to do too many robberies in too short a period of time. He is right to be concerned, as the police are staking him out already and photographing all his associates. A man known as 'the German' arrives, and there is a dispute about both his timekeeping and the share of the loot.

Regan identifies most of Tober's associates (who include the German, 'Doc' Boyd and 'Evil Willie' Sanders), but can't place a man with a moustache, who turns out to be called Jake. He believes that the robberies are in connection with a terrorist group that the German is involved with. Carter goes to DI5 to see if they know anything about the German's political activities, though he is brushed off by a somewhat supercilious Major Carver.

During the stakeout, Tober recognises Carter's driver Ingram and realises that his cover has been blown. Chief Detective Inspector Haskins orders Regan to arrest Tober, Doc Boyd and the German if they're found in the same place together again. Regan protests that there's not enough evidence for a conviction.

Tober tells the German that the police are onto them and that he's leaving. A fight breaks out, which Tober wins. He is just about to walk out when the German names both his daughter and the school she attends, blackmailing Tober into staying.

Carter returns to Milligan, persuading him to supply more information by threatening to arrest him for conspiracy. Milligan tells him that something will happen at 3.30 the next day.

Major Carver visits Regan and says that he is interested in the case, and that Regan should allow the gang's operation to proceed unhindered. Aside from a reference to "the national interest", he refuses to explain why. An angry Regan refuses to co-operate.

The German tells Jake (a fellow political activist) that the robbery is a fake, designed to catch the informant who has infiltrated the gang. It will be called off at the last minute, giving the German and Jake an opportunity to escape.

Haskins orders Regan to call off the operation, as Carver has explained to him that there is a DI5 mole in Tober's team. His identity is revealed when Carter recognises Jake as former Detective Sergeant Jenkins.

The robbery goes ahead. Regan initially respects Haskins' orders, allowing the gang to proceed unhindered, but then orders his men to give chase. This culminates in a shootout, during which the German is wounded and all the men are arrested.

Tober asks to see Regan, and tells him about the German's blackmail, and that if his daughter's safety can be assured he'll tell them anything they want. Regan is criticised by Haskins for disobeying orders. Carter rings Regan to say that Jake has escaped from hospital after beating him up. Major Carver clearly wants him to continue working undercover.