Series 7, episode 18
“A Deep Blue Goodbye”
Danny investigates the circumstances of an ex-NYPD officer who goes missing the day after she revealed to him that she had planned to make amends to the woman she and her partner wrongfully convicted years ago.
Also, Frank faces a dilemma when one of his peers, Chief Taylor Daniels (Isaiah Washington), refuses to retire, even though he’s hit the mandatory age limit, on the 150th episode of BLUE BLOODS.