This feature-length episodes starts with a gun being held by Lieutenant James Dempsey of the New York Police Department. He is sitting in his apartment waiting for his partner, Joey, to call. Dempsey's phone rings. It is Joey calling to tell Dempsey of their latest stakeout. They go to the docks where they suspect a drugs drop-off will take place. All of a sudden, Dempsey's C.O., Coltrane, turns up at the docks in his car. Another man at the docks stands up with a bag. The man at first heads towards Coltrane's car, but then walks towards Dempsey and Joey. Dempsey realises that he is going to be set up. Joey and Coltrane were going to set Dempsey up, but Dempsey reached for his gun and shot the man approaching him. Joey grabbed Dempsey from behind, while Coltrane made his getaway. Dempsey pushed Joey to the floor, turned round and shot Joey, who died.
Back at the station, Dempsey and his associate, O'Grady, are having an argument about Dempsey's situation. Dempsey was totally unaware that there was a corruption scandal until he discovered it. There was only one way to assure Dempsey's safety. It was here where Dempsey was seconded to a new undercover unit of Scotland Yard, known as SI-10, based in London, England. Once in London, he was partnered with Detective Sergeant Harriet Makepeace, who preferred to be known as "Harry". They were partnered together by the easily-irritated Chief Superintendent Gordon Spikings, who did not want any Americans in his department.
Their first case together saw Dempsey and Makepeace investigate caviar-smuggling and murder. Soon, Makepeace discovers that her uncle is involved in the caviar-smuggling. When their investigation is caught out, Dempsey and Makepeace are taken to an old disused apartment block, which was rigged with explosives. Luckily, Dempsey and Makepeace manage to escape just in the nick of time.