The fifth series of the crime drama spin-off focusing on an elite group of New York cops continues. This week, Goren and Eames expose a family’s shameful secret during their investigation into a series of church burnings.

When five churches are set alight in less than an hour, Goren and Eames are called in to examine the crime scenes. At St Gerald’s, they discover that a different modus operandi was used – a Molotov cocktail. The church was also the site of the only fatality – its secretary, Margaret, perished in the flames. The extent of the damage leads Goren to conclude that there are two firebugs working in tandem.

After interviewing the five priests and finding no major leads, the team is alerted to another rash of fires. Three more Molotov cocktails have been unleashed inside three churches, but with minimal impact. “Our dynamic duo’s getting sloppy,” observes Eames.

Further analysis suggests that St Gerald’s was the primary target. Goren notices that this blaze was formed in a more considered way, with four fires set in sequence along the aisle. It transpires that this is the route taken by altar boys in their procession. As the fire was started with fuelsoaked vestments, Deakins says that the perpetrator may have been “a kid with a beef against the church or the minister”.

With St Gerald’s in their sights, the detectives speak to its pastor, Reverend Poole. They learn more about Margaret, the arsonists’ only victim, and her role in the church. Reverend Poole describes her, saying, “She took things at face value. She saw scripture in black and white.” Concerned by Margaret’s seemingly simplistic view of good and evil, Goren sifts through her written correspondence and finds a torn-up note from new youth leader Justin Reid.

A visit to Justin’s home makes the detectives wary of him, as he openly flirts with Eames, despite the fact that he has a young wife and baby. He also comes across as an unlikely churchgoer, with his stockbroker background, extravagant lifestyle and womanising ways. A former altar boy at St Gerald’s, he had donated money towards its repair and admits that he sees himself as a role model. He confesses to knowing Margaret from his altarboy days, calling her an “odd duck”. Leaving the meeting feeling unsettled, Eames wonders, “If we find him creepy, imagine what Margaret thought.”

The detectives notice that Justin’s stepmother, Regina, bears a striking resemblence to his wife, Noreen. They speculate on the dynamic of the stepmother-stepson relationship. Justin was an impressionable teenager when his father remarried – perhaps Regina’s way of getting her stepson’s approval was to seduce him? “Incest as a motive for arson – of all the far-out theories I’ve heard in this office,” Carver muses. With a patchy theory on their hands and the family who may hold the answers remaining tight-lipped, the detectives face an uphill battle in finding the proof they need.