New York Police Lieutenant James Dempsey kills his corrupt partner Joey and has to lay low until the case can be further investigated. His superior O'Grady sends Dempsey to London, England as part of an exchange of officers. Chief Superintendent Spikings, head of SI10 is not to pleased to have a 'yank' forced onto his department. He decides to couple Dempsey with his complete opposite, Sergeant Makepeace, an upper class English rose on a case involving a mysterious shipment of caviar.
A heavy-duty Transit van carrying half a million pounds in used notes is hijacked, drivers and all - and S.I. 10 is tasked to find it. Meanwhile Spikings has his hands full trying to get Dempsey to part with his gun, as it is illegal for police officers in England to carry one.
Dempsey happens to be present at a casino when it is robbed and a security guard murdered. So, Spikings tells the Yank to wake up Makepeace in the middle of the night and start their investigation.
Dempsey and Makepeace are shadowing Frank Egan, who has just got off Scott free on a murder charge. His next big job seems to involve 'a bird man' and 'haggis'. It leads to Makepeace posing as a floozy and Dempsey as a pilot.
Frank Price is sprung out of jail, only to be killed by his accomplishes. Spikings suspects Price's boss Jack Lang, but when Lang's granddaughter Debbie is kidnapped it seems like someone else is trying to instigate a gang war. Meanwhile, Dempsey is more interested in wooing fellow American Angie Hughes.
Dempsey takes the place of American hit-man Schwartz to infiltrate a gang of drug dealers who lacing T-shirts with heroin. Little does he suspect that their main contact, Lei Shan carries a grudge against the real Schwartz. When Makepeace gets her hands on one of the T-shirts via one of her contacts, the undercover Dempsey finds himself forced to bump her off.
Jailbird Charlie Wilson wants to speak to Gordon Spikings alone concerning an urgent matter. But he shuts up tight after his little boy is kidnapped in the park. Meanwhile Spikings finds himself subject to a bombed briefcase while traveling by tube.
A priceless collection of jade artifacts has been stolen from Makepeace's ancestral home, Winfield Hall. When she and Dempsey join her father's other guest for a weekend pheasant hunt, the search soon turns into an old fashioned murder mystery.
Harriet Makepeace's best friend Sarah is raped and murdered on a train to London. The victim's father, Judge Hackett forbids an autopsy done on her body, leading the investigation to focus on one possible suspect seen by Makepeace: a slightly retarded man called John Bates.