Donnie Wahlberg announced that his Blue Bloods costar Bridget Moynahan will guest star on his spinoff Boston Blue. Wahlberg and Moynahan played siblings Danny Reagan and Erin Reagan on the original Blue Bloods. Moynahan will appear in the premiere of the spinoff and direct another episode later in the season.

Why so blue? Easing your transition from “Blue Bloods,” another familiar face will be popping up in the series premiere of CBS’ upcoming “Boston Blue”: Bridget Moynahan is set to reprise her role as Erin Reagan,