S5, E5: In the first of a two-part special, a private detective Peter Williams is found dead in a multi story car park. Everyone involved seems to have something to hide and as the case develops, DS Shap's career hangs in the balance due to his increasingly erratic behaviour. The team soon uncover the dodgy dealings of the PI company which Williams worked for. The disappearance of his friend and colleague Tanya Lucas has the team digging further into this world. Shap makes it a personal mission to find her while the rest of the team look into clients that Williams had been working for. It comes to light that Williams had been following Sally Jowell and her daughter Hannah on behalf of her ex-husband, convicted criminal Terry Camerton. Camerton quickly becomes a suspect, but furtive Shap, ahead of his colleagues, finds Tanya and then begins to pursue Camerton - but why is Shap so desperate to get to him first? Meanwhile, Janine discovers her son Tom has been truanting from school.