The police investigate an apparent break-in that results in the death of Derek Irons, his wife and youngest daughter. Two older children survived the attack but one is in serious condition and in a coma. Irons was a ruthless businessman who targeted his rivals' customers resulting in regular confrontations. Irons was stabbed but his wife and daughter were shot. Sam is reunited with an old friend from Northern Ireland, Det. Supt. Tony Ashton who is the senior investigative officer on the case. Harry assists the police with the death of an old woman who is believed to have fallen down a staircase. His post-mortem reveals evidence that is not consistent with a fall.

The police continue their investigation into the deaths of several members of the Irons family but based on the forensic evidence, they now believe he may have been killed elsewhere and then transported to his home. When one of Irons' two surviving children is killed, they look to his circle of friends and family for a possible motive. Thanks to Harry's information, the police investigate further into the death of an elderly woman who supposedly fell down the stairs in her home. Supt. Tony Ashton clearly wants to renew his friendship with Sam but she isn't so sure. Leo's home life is in turmoil and it's been affecting his work.