On the strength of evidence from a new witness, DCI Jo Davidson brings Terry Boyle back in for questioning about Gail Vella's murder. Kate is torn between loyalty to Jo and wanting to assist AC-12's investigation, and tensions increase when Kate encounters a face from the past with links to organised crime.

DCI Jo Davidson faces increasing pressure from all sides as AC-12 make major breakthroughs in the investigation, but an attempt to interview a key witness goes horribly wrong.