It's amusing to watch anytime someone can rattle Anthony DiNozzo Jr. and knock him off his wise-cracking, smooth-talking frat boy game, but no one does it quite like Tony Sr.

Last night's NCIS marked another stellar performance by guest star Robert Wagner as the DiNozzo patriarch, who again ended up in the middle of a murder investigation.

When it became clear that he was the team's best shot at uncovering the whereabouts of a "Broken Arrow," working undercover with Ziva no less, Tony Jr. almost lost it.

Michael Weatherly (Tony Jr.) and Robert Wagner (Sr.) are hilarious to watch.

Only NCIS would attempt an episode pertaining to a lost nuclear weapon potentially sold on the black market while keeping the mood lighter than most weeks, and have it work.

This speaks to the show's stellar writing as well as acting chops of Mark Harmon, Michael Weatherly and Wagner, who somehow comes off as a good guy despite his sleaziness.

The self-proclaimed "plane whore" arrived in D.C. on a private jet from Switzerland with Woody Iverson, a former Naval officer and high-ranking employee at Royce Global Group.

Iverson was killed right before a meeting with Admiral Chase, a member of the Joint Chiefs of Staff. Whatever he new was apparently very valuable. So how did Tony Sr. fit in?

Because he knows the reclusive founder of Royce Global and his right hand man, Dan Mayfield, Tony Sr. scored an invite to a black tie event kicking off the annual Royce Summit.

That's where wheelers and dealers from shipping, mining and even arms dealing circles meet to exchange ideas (and potentially other bad stuff). He was their ticket in. With Ziva.

This drove Tony Jr. up the wall, but Gibbs was all for it, although he made clear he doesn't like Tony Sr. because of how his lifestyle hurt (and still hurts) his relationship with Jr.

Watching the elder Tony rack up massive bills on NCIS' dime may have irked his son (and Fred from accounting), but his shameless, comedic flair in doing so was just classic.

Meanwhile, we learn that Mayfield and Royce's head of security, Gaston, had found a lost nuclear bomb from the 1950s, and were in the process of getting it off the seafloor.

Rather than informing the government, which our victim apparently tried to do, they planned to sell it to the highest bidder at this symposium and peace out on the company.

Tony gets a look at his gorgeous future stepmom.

Looking absolutely beautiful, Ziva infiltrated the party and Tony Sr. certainly acted the part of her well-heeled escort. Then things got scary when a foreign national made her.

One of the best lines of the night came from Gibbs, who answered "she is a weapon" when asked if she was armed. Sure enough, Ziva roundhouse kicked her way out of the jam.

At the same time, Abby found DNA evidence pinning the murder on Gaston, with an assist from Mayfield, who was keeping Royce on life support long enough to seal the deal.

In a way, the murder investigation felt hastily tied up, but only because it played second fiddle to the terrific Tony-Ziva-Tony dynamic, which was a rare treat. We can accept that.

Besides, what's not to love about the episode-ending heart-to-heart between father and son, reminiscing about fishing and pledging to be honest with each other from now on?

Such a great scene. This was right before Sr. bummed a ride to the airport from his son so he could con his way onto Donald Trump's plane, of course. Hey, progress takes time.

Random thoughts and observations:

• Abby's plea to give Tony Sr. a chance was heartwarming in what she revealed about her own father, and how she never got to know him. Character moments like this really make the show, even though they're almost in passing.
• Gibbs had some terrific non-verbal interactions, be it motioning Ziva to go after Tony, straightening Ducky's tie or hastily kissing Abbs before racing off with her findings.
• McGee's right, Ziva's passport photo was pretty hot.
• That was a good time to pull the Probie card.

What did you think of last night's NCIS? Comment below!

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.