Taking one unexpected turn after another and continuing to raise the stakes, Tuesday's NCIS: Los Angeles was one of the best standalone episodes the show has produced to date.

"Empty Quiver" began with Sam and Callen undercover as CHP officers (so glad they didn't just drop that after last week), tracking the Golden State Taxi Service smuggling ring.

When they finally infiltrated it, they found more than anyone bargained for.

The plot was complicated at times, but realistically so. Any effort to pull off what this group of miscreants nearly did would require many interconnected conspirators and steps.

The ring leader, Pat, was a former CHP officer who started a gang to assist smugglers and criminals by providing them safe passage along a major stretch of U.S highway.

Why? Hard times drive people to desperate measures.

Callen and Sam find him dead, and Pat's second-in-command, Jennifer, reveals that he was just approached about a job with a huge reward, but when he said no he was killed.

NCIS has her put the word out to whomever is orchestrating this huge operation that the Taxi Service is back in, and that her two best men (Sam and Callen) are on the case.

What followed was an ambush of epic proportions.

All they have to do, says the businessman calling the shots, is stop the SUV of a business rival and arrest him. The team doesn't see the connection to its case, but complies.

The assault that followed nearly left Sam and G dead. You have to wonder if they could realistically escape, even with their training, considering how outnumbered they were.

Rarely is a scene on network TV as terrifying as this:

While I don't keep track of such things (maybe I should), I doubt there has ever been an NCIS: LA episode with a higher body count or with higher stakes than "Empty Quiver."

The title refers to a nuclear weapon that goes unaccounted for. The SUV actually carried the businessman's crew, whose real plan was to hijack a nuke in the truck behind them.

The connection to the Marines was intelligence-related. They knew where and when a warhead would be traveling by truck on its way to be refurbished, and they procured it.

You don't just drop one of those things off a building and run for it, however, so the terrorists also kidnapped a young physicist to activate the warhead ... or so we thought.

It turns out this was all a ruse. The quiver was empty, yes, but the businessman and physicist were conspiring to create mass hysteria, not mass casualties, and cash in on it.

The threat of a nuclear weapon on the loose and being set off in a U.S. city would cause a major Wall Street sell-off, allowing them to short sell stocks at ridiculous profits.

Fortunately, Eric shut down the entire Internet (hey, they did it in Egypt, and if anyone can do it in the U.S., it's him) before the video could leak on the White House's page.

Meanwhile, the most bad-ass NCIS agent of all time, Kensi, single-handedly took out the ex-military crew who stole the nuke. With assists from Callen and Deeks, of course.

With a couple of firefights that exceeded even NCIS: LA's high action standards and the intensity generated by a nuclear weapon being on the loose, this was gripping drama.

I jumped out of my seat or cowered in fear at least three times over the course of an hour, a testament to the direction and to growing attached to the characters put at risk.

There were fewer lighter moments than usual this week, but Kensi and Deeks made the most of them. Their odd-couple partnership continues to be a highlight of the show.

Deeks' most terrifying moment all night came not when staring down the barrel of an automatic weapon, but when Kensi laughed in an effort to be laid-back and "hilarious."

There was no "that time," right, Nell? Didn't think so. But we love her anyway.

What did you think of last night's NCIS: Los Angeles? Discuss!

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