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[SPOILER ALERT: The rest of this story contains spoilers for “NCIS.”]

There is a dead Marine and a drug case on the "Personal Day" episode of "NCIS," but the hour is really about whether or not Gibbs is ready to move on, and if his team can accept how he's changed since his near-death experience.

We begin with Ellie Bishop (Emily Wickersham) and Tim McGee (Sean Murray) gossiping about Gibbs' new look, but Tony puts a halt to that, saying, "He got shot, he's back, he's different. Who wouldn't be?" Meaning they should accept the change in Gibbs. Only Tony is having trouble taking his own advice.

Tony's concern grows when Gibbs agrees to work with DEA Agent Luis Mitchell (guest star John Gabriel), who has a case that went cold in San Diego and he tracked the bad guy to D.C.

Gibbs doesn't mention that he and Mitch have history -- tragic history. But Tony discovers that Mitch's father Kurt Mitchell was the agent who died protecting Gibbs' wife Shannon and daughter Kelly. When Tony talks to Gibbs about it, he says who Mitch is, is not Tony's concern. Tony tries to get Gibbs to turn the case over to another team -- and even finds one. But Gibbs won't be moved.

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The team gossips about Gibbs' (Mark Harmon, pictured) new look after he replaces his standard military haircut and polo shirt for a modern cut and tailored dress shirt, on NCIS, Tuesday, Sept. 29. (CBS)

Later Gibbs tells Mitch a story, which explains why: We learn that Mike Franks (Muse Watkins) had been protecting Gibbs' family, but it got too dangerous for him, so he asked for a volunteer to replace him. And Kurt volunteered, saying, "I would want someone to do the same for my family." So, Gibbs tells Mitch, he isn't going anywhere. And now we understand the debt.

But it's even worse, Benson Long (Robert Knepper), Mitch's Moby Dick, the drug cartel bad guy he has followed to D.C., turns out to be the man who ordered the hit on Gibbs' wife Shannon and daughter Kelly, resulting in the death of Mitch's father.

Tony once again confronts Gibbs, but Gibbs insists that they are going to get Long on good evidence. Tony says maybe not. They just pinged his phone and Mitch is not where he said he would be.

With his case falling apart -- the Marine who was supposed to provide Mitch with evidence against Long turns up dead -- and the one lead they got from that that took them to Long's cousin's store didn't pan out. So Mitch is at his wit's end and decides to kill Long.

Meanwhile, Tony and Ellie track down a poker-playing buddy of Long's cousin and blackmail him into going back and playing poker one more time -- and they give him a gift to give Roy. It's a poker chips set.

Long finally returns home to find Mitch and Gibbs waiting for him. They inform him of the death of his cousin, and when Long mocks them, Mitch aims his gun at Long's head.

But Gibbs talks him down, saying, "You know what I did and it didn't do a thing. It didn't bring them back." He is referring, of course, to the fact that he killed the man who shot his family.

Then, McGee and Tony come in and arrest Long. The chips set they had Highland give to Roy was bugged, and it has Long admitting to the killing on it.

The case may is closed and Gibbs is heading to San Diego, but Tony comes by to talk about Iraq. Gibbs still isn't ready to deal with that and instead asks Tony, why he is still there. He reminds Tony that he turned down an offer to lead his own team made to him years ago. Gibbs says that he had a reason why he joined NCIS, and while things change, his reason hasn't. And he puts it back on Tony: "Either you've got a reason, or you don't."

Cut to Gibbs finally taking his personal day, so he and Mitch can scatter Kurt's ashes in the Pacific Ocean, each lost in their personal grief.

As if that isn't sad enough, Gibbs goes to the house where he lived with his family, and uncovers a bird bath with three handprints in the cement: his, Shannon's and Kelly's.. He lays his hand on top of them. Memories.

"NCIS" airs Tuesday nights on CBS.