NCIS comes under attack by a mysterious enemy from the past. Also, Vance tries to mend fences with his estranged son by explaining why, despite the ongoing dangers of his job, he still chooses to stay at NCIS.

Country powerhouse Keith Urban is enlisted as Mega Mentor to help prepare the artists for the Knockouts. The coaches pair two artists to perform solo against each other, then select a winner to move on to the Playoffs. Each coach has one steal.