Len Cariou reprised his Blue Bloods role as Henry Reagan in Friday's episode 13 of Boston Blue season 1. The patriarch arrived in Boston to support grandson Danny's transition to the Boston Police Department. The episode also explored Mae's family secrets amid a shooting involving Rev. Peters.
Henry Reagan, played by Len Cariou, made a guest appearance on Boston Blue, reuniting with his grandson Danny Reagan and great-grandson Sean, who was on duty in uniform. Henry remarked to Sean, 'If your grandfather could see you now....' referencing Tom Selleck's Frank Reagan from Blue Bloods. The visit began lightheartedly as Henry caught up with old cop friends in Boston, known as Beantown. The episode centered on a case where Rev. Peters was shot in crossfire but survived. Mae's older sister Jill, portrayed by Holly Robinson Peete, arrived, leading Mae to uncover that their mother died by suicide from a drug overdose, not a car accident as she believed. Rev. Peters had shielded Mae from the truth, with Jill agreeing to the cover-up. Mae, still processing her husband Ben's murder and her father's recent shooting outside church, told Jill she needed time. Henry's true purpose emerged at the Silver residence: aiding Danny's move from NYPD to Boston PD. He revealed a friend at Boston HQ noted a lieutenant with Danny's old shield number from 25 years on the job. Henry offered a 25-year-old bottle of scotch for a trade, allowing Danny to keep the number, which moved him to tears. Danny must still serve a uniform shift before detective duties, an idea series co-creator Brandon Margolis plans to explore later in the season.