Father and son Bill and Frankie McAteer are killed in a horrific car accident on their way home from work at Billingsgate Market. Nikki and Jack arrive at the scene of the crash to meet DS Jodie Tanner, and to discover Frankie's body still in the car but riddled with bullets. Whoever was driving the SUV had a gun.

Back at the Lyell centre, Nikki's post mortem examinations suggest that Frankie was the target, rather than Bill. Clarissa and Max discover a deleted video on a mobile phone showing a sexual encounter between Frankie, his girlfriend Becky and best friend Liam, which was posted on a revenge porn website. However when Liam is also killed, the video becomes the key to the killings.

When Nikki and Tanner visit Becky, her flatmate Paul enters and she bursts into tears about the murder. But Paul looks like he has worries of his own…

Meanwhile, Clarissa's husband Max is an expert in the fast-developing field of digital forensics and lends some equipment to help crack Frankie's seemingly-empty phone, his arrival causing an icy reaction from both Thomas and Jack.

Nikki travels to Mexico to attend the funeral of Luisa, a former intern at the Lyell Centre who was murdered in a carjacking in her native country. Nikki soon stumbles across the post mortem report and realises that the body is not Luisa's. There's been some kind of mistake - or is this something more sinister?

Assisted by Dr Eva Vasquez and fired up with the idea that Luisa might still be alive, Nikki and Jack trace her last known movements and are led to a farm where a cartel massacre was carried out, where they start to perform makeshift post-mortem examinations.

By now, Nikki and Jack are gaining the wrong kind of attention. And when Nikki goes missing, Jack is forced to make decisions that will end in life or death…