The team enlists an old friend when a crime boss is murdered, triggering revenge killings across the island; MacGarrett and Danny work out details concerning their new restaurant venture.
Nell goes under cover as replacement for a dead Defense Department researcher; the new NCIS assistant director questions Hetty's leadership.
Magnum and Higgins help an up-and-coming mixed martial arts fighter who is being pressured by a gang to throw an illegal fight.
At Allison's insistence, Ken joins a civic-minded community group that may not be what it seems.