Season 4 sees DI Max Arnold and DS Layla Walsh return to tackle four new murders within the elite world of Chelsea β a fashion mogul sinking fast in the trappings of her wealth; an aristocratic dynasty guarding their bloodline with brutal devotion; and a wellness and beauty salon owner concealing lethal truths β all falling under the relentless scrutiny of our duo. This season also features a cryptic double-murder that begins in Chelsea and spirals outward, drawing our team into the cut-throat world of architecture. The regular cast return to crack each case and β while a hint of romance is in the air for Max β as ever, the road to justice is anything but smooth.

Butler Lucas is found dead in the Thames. The investigation gets complicated when the team learns that Lucas wasn't Lucas at all - he was Billy Paige, an undercover journalist investigating the household of self-made fashion mogul, Clare Curtis.

When notorious gangster Trent Wilsher is found shot dead and the prime suspect, Rory, Earl of Davenstock, disappears, DI Arnold must launch a manhunt to find him before Trent's brother takes revenge on the remaining Davenstocks.

Sonia Blessing is found killed in her own salon. DI Arnold interviews an old boyfriend and scorned clients, but the truth behind Sonia's murder appears much darker, revolving around a hidden identity and a desperate attempt to escape coercion.

Famed architect Rowan Jameson is thrown from a hotel balcony in Chelsea. Two days later a university employee is strangled in Rowan's hometown Cambridge. Might the two murders be linked by controversial development plans at St Cuthbert's College?