Gene and the rest of CID are feeling the pressure to stop a series of politically motivated arson attacks in the lead up to the 1983 General Election, after a military compound and a polling station are set alight. DCI Jim Keats announces his plans to monitor the way Hunt and his team work while trying to turn each member of of the team against Gene. Elsewhere, Alex continues to mount her investigation into what really happened to Sam Tyler in 1980 and is struggling to work out why she is being haunted by the young police officer.

Gene discovers that an undercover operation to catch several drug dealers is taking place on his patch without his knowledge. Determined to take control Hunt blows the cover of an undercover operative who turns up at CID and is eventually placed under his protection, yet it seems someone on the inside is twisting things to help the drug dealers stay out on the streets. Meanwhile, the deceased police officer continues to haunt Alex. Could he actually be her key to getting home?

When DCI Gene Hunt's former Manchester colleagues, DCI Litton and DI Bevan, turn up on his patch he immediately smells a rat. They're in pursuit of northern comic Frank Hardwick who's wanted for stealing 2,000 pounds from the Police Widows Fund. However, their desperation to track him down leaves Gene and DI Alex Drake suspicious of their real motive.

DCI Jim Keats has almost finished his report into DCI Gene Hunt and his team, but he's still pushing DI Alex Drake to find out what really happened to Sam Tyler. When reports come in of a disturbance at an ANC illegal drinking den Gene heads in all guns blazing. The men at the club are quick to dismiss the disturbance as nothing, but when DI Ray Carling spots blood on the floor and discovers a dead body, it leads Gene into a murder investigation.

DCI Gene Hunt and his team are investigating a diamond heist following the murder of three London gang members. But DI Alex Drake is distracted and, with encouragement from DCI Jim Keats, she decides to pursue her own investigation to the bitter end - did Gene Hunt murder Sam Tyler? When Gene discovers that Alex has gone, he races after her leaving Ray Carling, Chris Skelton and Shaz Granger to plan an ambitious sting operation. As Gene desperately tries to reach Alex before she discovers the truth, Chris, Shaz and Ray's world completely falls apart. It's time for Alex and the rest of the team to find out the truth about Gene Hunt...