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...