After being awake for four days, Tony thought his mind was playing tricks on him when he glimpsed an informant who he hadn't seen in 15 years. 

In between flashbacks to those earlier years, the question persisted on NCIS this week: what was keeping him awake?

"Once a Crook" began with a murder case that turned out to be peripheral to the main story. 

Anton Markin - a thief who was recruited by Tony 15 years ago to inform on a mobster named Victor - returned home to comfort his grieving sister Marie. Years ago, Markin had killed Victor's brother in an act of self-defense, after which he fled. Vincent, upon learning of his return, had Marie kidnapped in an effort to take vengeance on Anton. During the kidnapping, Petty Officer Wells was killed. 

Man, there was so much going on with this episode, all in an effort to get to the heart of the matter (well, if we're counting, that would be two hearts): Tony's relationship with Anton and Tony's sleep deprivation.

Tony's flashbacks showed him to be a caring and vigilant member of the police force - keen to do the right thing by his informant, while catching the bad guys. He truly wanted to have Anton's back, despite his lack of experience at the time. Anton knew that Victor was going to try and kill him but Tony seemed sure he could keep Anton safe. It seemed a little surprising that the streetwise Anton knuckled under to Tony, even though he was sure Victor was out for his blood. Maybe that's the power of Tony we're seeing here, a man who will talk you into walking into a den of snakes, while assuring you that they're harmless and only want to play.

Far more interesting was the sleep-deprived Tony.

There are a number of possible reasons about why he couldn't sleep (or was it that he didn't want to sleep?) for four days. Obviously, he misses Ziva. Ironic that this happened:

Tony: It's so interesting. No one will say her name. Have you noticed? It's like she's dead. Every time I look at her desk, every time I close my eyes....I just feel like I made a mistake. Like I made the wrong decision. Only it wasn't me who decided. So yeah - I'm probably wrong to think Anton's innocent in all this.
Gibbs: I'll trust you any time. | permalink

Yet even he didn't mention her name. No one did, during the whole episode.

Is it just that he misses her? Or is it that he has regret for not doing something he should have, like trying harder to convince her to come back? Or like making a decision to stay there in Israel with her? My guess is that all of these questions are whirling around in his head ... so much so that he tells Ducky that he's worried that he's losing it.

I'm continually impressed by Gibbs' character: he knows when to crack the whip and he knows when to stand still and listen, as he did with Tony in the washroom. His words of encouragement were honest: you followed your gut and I'll trust you anytime. Powerful, important words that Tony needed to hear.

Observant fans will have noticed that there were at least two occasions when Tony said something that had two meanings. The first was in the washroom when Gibbs had to ask: are we still talking about the case?

The second came near the end of the show when he told Anton that he wanted to help:

Tony: I want to help.
Anton: One thing I've learned, Tony. Just because you want it doesn't mean it's going to happen.
Tony: Tell me about it. It's funny - never stops me from trying. | permalink

I almost missed it myself. When Tony hesitated and then said tell me about it you sort of knew he was referring back to Ziva. Then, when you add to that his statement that it never stops him from trying, it may mean that the Ziva story is not over. Sure, nothing's happening in the near future, but I think this is the writers letting us know that the door is still pretty much wide open.

Some final notes:

• We got to see Delilah again. She seemed to fit right in like a glove didn't she? Joking when she shouldn't (maybe her jokes will go down better once Tony gets some shut-eye); finally getting under Abby's skin; and making friends with her. And we saw McGee smile a few times at her. She's not taking Ziva's place but... maybe it wouldn't have been such a bad thing if she did? 
• Christopher Silber, who wrote this episode, made good use of a single item which served to act as a hinge between the Tony of today and the Tony of 15 years ago: a piece of grape-flavored Choward's Scented Gum. Nicely done. Even Delilah got in on some of that.
• Gibbs (concerning Deliah): she's just trying to be nice.  Abby: I know. It's freaking me out, man. 
• As always, check out our extensive list of NCIS quotes for this episode.

Over to you: what was Tony's real issue? What was it that kept him awake, and more importantly, how was he able to sleep after the case was solved? Was Anton a proxy for Ziva? Was it that if he couldn't resolve the Ziva question, he at least could bring Anton and his sister together? What did you think of the overall episode?

Douglas Wolfe was a staff writer for TV Fanatic. He retired in 2016. Follow him on Twitter

.