Top lawyer Richard Fleet is shot in the head in his car after a late business dinner with his partner Charlie Muir and client Simon Turner, the MD of building company Arcadia. Despite the gun being left at the scene there are few clues for the team to go on. Reid and Burke visit Fleet's widow, Adele, and are shocked to discover that not only are they faced with a less than sympathetic wife but that she is also having an affair with his business partner Muir. Neither have alibis for the time of the murder and fail to mention Fleet's £5m life insurance policy. Residents Betty McGoldrick and Martha Ramsay are protesting against the new phase of housing development. They believe that a pharmaceutical company once stood on the site and that chemical contamination has already caused a spate of illnesses, including Martha's son Ben who has leukemia. The women inform them that the case was thrown out of court and to Burke's surprise he discovers that Fleet and Muir represented the residents and not Arcadia – despite being on Arcadia's payroll. When Muir is shot on the Arcadia site and another identical gun is found near the body, Burke begins to suspect Turner. However, his suspicions are without cause when Turner is later found shot dead in the Fleet's home, again with a gun at his side. As the team start to unravel the mystery, an unnamed fourth man is discovered to have been at the restaurant on the night of the first murder. But can a paralysed Muir help them find the guns, the killer and the identity of the fourth man?