The fifth series of the crime drama spin-off focusing on an elite group of New York cops continues. This week, Logan and Barek’s investigation into a series of gruesome home invasions leads them to a local foster mother (guest star Whoopi Goldberg).

When the members of a wealthy Staten Island family are found murdered at their home, the detectives on the scene are shocked by the grisly discovery. “It’s like Charlie Manson in there,” warns a policeman as he shows Logan and Barek inside. The family has been slaughtered by burglars armed with machetes, and a number of valuable art objects are missing.

It transpires that the intruders knew their way around the house because they had taken a ‘virtual tour’, available online through the family’s estate agent. When the detectives check the website, they discover that a Brooklyn teenager had been searching the site for hours –most likely to ascertain which house to hit next. The teenager is identified as Antonio Mattini, whose DNA is found on a broken earphone left at the scene of another home invasion.

A Brooklyn cop puts Logan and Barek in touch with Chesley Watkins (Whoopi Goldberg), Antonio’s foster mother. She offers to help the detectives, but claims not to have seen the boy since he left her care two years ago. When she asks why the detectives are looking for her son, Logan replies cryptically: “Let’s just say he’s not one of your success stories.” “He’s one case I never cracked,” acknowledges Watkins, sadly.

The detectives stake out the Queens restaurant where Antonio works. As they await backup, they see three men enter the premises and attack Antonio, before a fourth man comes in and tries to help the boy. When the trio turn on the newcomer and the altercation gets out of control, Logan and Barek realise that there is no time to wait for their backup to arrive, and go in. The fourth man points his gun at Logan, who is forced to shoot when his warnings that he is a cop go unheeded. Logan is devastated when he finds out that the man is also a cop – undercover agent Bone Tarkman, who later dies in hospital.

Captain Deakins gets grilled by Internal Affairs about the shooting, but defends his detective’s actions. “It’s a lousy situation, but Logan was by the book,” he insists. “I got two home invasions. Two butchered families. I need him back.” The shaken Logan is cleared, and rejoins the case.

It then emerges that Tarkman was also fostered by Chesley Watkins – at the same time as Antonio – as were the three men who attacked them in the restaurant. As Chesley is the common link, the detectives wonder if she lured Tarkman to the restaurant to be killed by her other foster sons, who they now suspect of carrying out the home invasions. But when Barek and Logan talk to Chesley at her home, she denies that her boys could be responsible. “Monsters did this,” she says, looking at the photographs of the bloody crime scenes. “I didn’t raise monsters.”

Cracks appear in Chesley’s story when the detectives uncover evidence that she was helping the boys decide what to steal from the houses. When they follow the trail to her foster son Floyd Bolton, the detectives find four machetes in his car and bring him in. Floyd tells the detectives that Chesley masterminded the home invasions, but without corroborating evidence from his foster brothers – or a confession from Chesley herself – the case is shaky.

Things get even worse for the prosecution when Floyd leaps to his death after the arraignment; and Antonio, who was sent to prison after his mother turned him in, is stabbed to death. With no star witness, and the other two boys keeping quiet to protect their puppetmaster, is the case set to slip through the detectives’ fingers?