In the latest episode of Boston Blue Season 1, Episode 17 titled 'L'dor Vador,' Bridget Moynahan reprises her role as Erin Reagan, Danny's sister from Blue Bloods. The episode features Danny escorting Erin back to New York amid family tensions over his move, alongside major revelations in Lena Silver's family storyline.
Danny Reagan, played by Donnie Wahlberg, accompanies his sister Erin Reagan (Bridget Moynahan) to New York City for a Reagan family dinner at the end of Friday's episode. Before the off-screen dinner, the siblings apprehend a serial killer named Abraham (Erin Gann) and rescue his latest victim. Abraham needles Danny about his relocation to Massachusetts, exposing Erin's resentment and prompting her to admit the family is not entirely supportive of the move. Erin later insists she was misleading Abraham, though her conviction wavers, noting everyone would be thrilled to see Danny, at least for one Sunday since his pilot episode departure to Boston. Abraham also misleads them about the victim's location and mentions Danny's brother Jamie to provoke him further. On a separate front, Lena Silver learns the truth about her biological father during Rev. Peters' heart operation morning. Mae reveals Chris Williams (Erik King), an ex-con arrested for armed robbery, as Lena's father, whom she never informed of the pregnancy. Lena discovers independently that Williams reformed and now serves as a small-town police chief near Boston. She confronts him at his precinct but meets Detective Asher Reed (Douglas Nyback) instead, unaware of their connection. Chris arrives at Mae's after Reed's tip-off, admitting he knew about Lena. He discloses another daughter, Christina (Alisha Wainwright), making her Lena's half-sister. Christina arrives at the precinct to meet her husband Reed—Lena's brother-in-law—prompting Lena to exit quickly upon realizing the ties. Erik King and Alisha Wainwright will each return for one more episode this season.