A hung-over Regan pulls local Lothario Lukey Sparrow for his part in the theft of thirty thousand pounds worth of mercury. The boy has an alibi - he was in bed with a married woman, but wants it kept quiet, as he is getting wed next day, to Linda, daughter of the fearsome Lily Rix. Regan proves Lukey's part in the crime but needs to reach him before some very dangerous heavies do. Either way the wedding seems unlikely to go ahead, subjecting Regan to the full wrath of Mrs. Rix.
Dour Scots sergeant Davy Freeth arrives from Glasgow in pursuit of three villains who, he claims, have come to kidnap somebody, but he will say no more, even when one of them is found dead. Regan is patronising towards him, calling him Jock, but when a kidnap attempt on a little girl is bungled and the girl escapes, Freeth annoys Regan by admitting he has known all along who the real intended victim is - the daughter of a Scots heavy, Boyd, living in London, and Freeth has tipped him off about the surviving pair. Between them, Boyd and Freeth do Regan's job for him ...
A daring gang of cold-blooded thieves make off with lorries carrying brandy on two separate occasions, killing a driver and injuring a policeman. The Sweeney are made to look a laughing stock at their failure to catch the gang. Carter's new girlfriend Julie Kingdom and her colleague Mike Seton, both young uniformed rookie cops, go out on a limb to pursue a known fence, and recover the brandy. However, Regan is into damage limitation and wants to take the credit for himself, putting him at odds with Carter.
A burglar falls to his death from a roof and another gang member, 'Red' Redgrave, feels he should have saved him but his sight is failing. Furthermore his estranged wife is about to marry someone else and he is having doubts all round about his life. Regan is fairly sure that Red's gang are about to carry out another burglary and yet Red seems to be deliberately pointing Regan towards catching them. Regan wonders what Red's motives are.
A lorry containing cigars is hi-jacked, and the driver and one of the robbers are killed. The gang is, in turn, attacked and wiped out by another, Irish gang, led by Farrell and Flynn, because some of the cigar-boxes contain drugs, which the I.R.A. are planning to exchange for a new model of gun with laser sights. Regan traces the gang via the sale of some stolen cigars and the trail leads to a house in the country where the Irishmen are expecting a plane to arrive. All along Regan's girlfriend Jane has been having bad dreams about harm coming to him and she may well ...
Eddie Monk has been straight for some years and he and his wife are good friends to Regan. He wins the pools but is blackmailed over a robbery for which he was never caught eleven years earlier and is killed after a fight with the blackmailer, Fischer. Using leads from a former gang member and his old mentor, Regan tracks down Fischer and has his revenge. Haskins is less fortunate when an important witness is put out of action.
Regan is staking out vicious robber Vic Tolman and his girl-friend Lyn Hurst, who have stolen the wages from the firm where Lyn worked. A surveillance is in progress on the flat belonging to Lyn's sister Joan, who is looking after her daughter. Regan and Carter eventually break into the flat and use the two women as bait for Tolman. He turns up but things do not go as planned.
Tycoon Leonard Gold is being blackmailed by Harold Collins, who has a photo of him present at a massacre of civilians in Malaya when he was in the Army twenty-five years earlier. He appeals to ex-commanding officer Masterson, who, with two mercenaries, breaks into a bank vault and steals the photo and other evidence. However, the job done, Gold finds that Masterson is an even more dangerous blackmailer than Collins.
Regan absents himself from the stakeout of a gang who rob wealthy tourists to come to the aid of Alan Ember, who, years earlier, had been a helpful informant. Now a rich businessman he has had a phone call to say that his son Paul has been kidnapped for a ransom of ten thousand pounds. Against Regan's advice Ember pays the ransom and the boy is returned, but the reunion soon turns sour.
Jimmy Fleet cons two businessmen out of a cache of diamonds, which he hides before being arrested and remanded in Wormwood Scrubs. Carter goes undercover as his cell-mate and gains his confidence and when Jimmy is released for lack of evidence the two go on a drinking spree, rudely interrupted by Patsy Kearney, a villain who steals from other villains. The Sweeney come to the rescue. Jimmy is unaware that his girl-friend, who is supposed to have the diamonds, is double-crossing him and, when he arrives at her empty flat, assumes that she has been captured, causing him...
A burglar is found dead of the home of Professor Busby, though nothing appears to have been stolen. Government official Bellcourt tells Regan and Carter that Busby was working on pills to relieve heart disease and that the burglary was no doubt master-minded by Danilov, the opponent of a head of state friendly to Britain who would benefit from the pills. Busby goes on the run, entrusting his supply of pills to his girl-friend Wendy, who works with comedy duo, Morecambe and Wise. They in fact end up with the pills and are pursued by villains and Sweeney alike, ending ...
As Doctor Delacroix, an apparently respectable gynaecologist, is leaving his clinic on his way to the airport, he is jumped on by a gang of thugs in a car and robbed of his suit-case. He is initially reluctant to disclose the contents of the case, which turn out to be untaxed monies which he was hoping to smuggle out of the country. Regan's investigations lead him to villain's glamorous girlfriend Christobel Delgado, a Latin lady, but she is definitely not what she first appears to be.
Detective Sergeant Taylor is shot and wounded, and names his informant, Jimmy Park, as pulling the trigger. Regan visits Park's girl-friend Eve, who says that Taylor was corrupt, and gives her tail the slip in order to give money to Park, who is lying low in an old disused warehouse. Regan eventually tracks him down and more shots are fired. At the same time Haskins is having problems with his wife as she starts to lose her grip on reality and live in the past.
A security guard is murdered during a payroll snatch. The local police force under Chief Superintendent Canning have no luck in catching the robbers and Canning is reluctant to work with Regan when the Sweeney are called in, frequently clashing with him. When Regan apprehends all the gang without telling him, Canning is far from happy. Regan is accused of corruption nine years earlier and Canning, his contemporary, refuses to help him. Fortunately Carter finds someone who will, but the whole experience leaves Regan extremely bitter.