Person of Interest, which is currently airing a tremendous fourth season on CBS, is one of the most successful trojan horse series in television history.

What began as something that seemed like just another CBS detective show — albeit one with a pretty cool premise, in which two mysterious men hunted down people who were either about to become criminals or the victims of crimes, based only on their Social Security numbers — has slowly and steadily grown into a sustained critique on the American security state and a musing on a post-human future, where acolytes of various godlike artificial intelligences offer their worship and supplication.

Yes, this is airing on CBS. Yes, your parents probably watch it every week.

But what the fourth season has suggested is that what Person of Interest has been most successful at is becoming the new X-Files. It's appropriate the latest iteration of Mulder and Scully's adventures should end up on CBS. After all, the entire network was built atop the back of that show's alien-hunting adventures.

A brief history of ‘80s cop shows

To understand why requires a brief history of TV cop dramas. In the year 1981, the genre's evolution bifurcated along two lines. The first was driven by the new series Hill Street Blues, which looked at the home lives of its cop characters, as well as the social ills of the blighted urban neighborhoods they worked in. The second was the cop show as it had always been practiced: a handful of officers and detectives solving a case every week.

The Hill Street Blues imitators had their cases of the week, to be sure, but they also borrowed many techniques from soap operas and other serialized storytelling models. As such, the closed-off cop shows — which came to be known as procedurals (because they focused more on the "procedure" of solving a case than the characters) — started to fall out of favor.

Procedurals never entirely disappeared — hello, Law & Order — but by the middle of the ‘90s, they were largely anomalies on the TV landscape. Even in the Nielsens, the biggest shows of the era — ER and NYPD Blue, for instance — were in the Hill Street model. (Law & Order would become one of the biggest shows on TV, but it grew very slowly and flirted with cancellation in its first few seasons.)

Of course, there was a show on TV very interested in the procedure of solving crimes. They were just crimes that involved monsters, and the procedure involved a hefty dose of pseudoscience. The X-Files was one of the most popular, influential shows of its era. Mulder and Scully received critical plaudits and Emmy nominations. They graced magazine covers and spawned novelty pop hits.

And this was all totally justified! The X-Files was perhaps the most cinematic, most inventive show of its era, like nothing else on TV. Its early experiments with serialization in its long-running alien conspiracy storyline had great influence as well.

But at its heart, it was basically a pre-Hill Street Blues cop show, where the monster was identified — but not always caught — in every episode. (Notably, creator Chris Carter's primary influence was Kolchak: The Night Stalker — a ‘70s show.) The show took the best things about those earlier cop shows — notably, a willingness to tell weird, close-ended stories — but added a healthy dash of everything Hill Street had done well — evolving character relationships and serialized stories.

Nobody could quite copy the show or its success, though many tried. It seemed sui generis, a weird reflection of the ‘90s that would remain there — until CBS actually managed to make an ­X-Files clone that didn't seem like an X-Files clone. It was called CSI, and it changed television.

The X-Files with sci-fi

Go back to early CSI after watching a couple of late-period X-Files episodes. Strip out the monsters, and replace them with gruesome killers, and the two shows are all but identical.

The mistake so many X-Files clones made was in trying to top the show's sci-fi or conspiracy elements. The genius of CSI creator Anthony Zuiker was how he simply replaced the pseudoscience of X-Files with slightly more plausible pseudoscience. CSI relied less on serialization, but had pinches of it here and there. And that affected its entire network.

X-Files with kidnapping? That's Without a Trace. X-Files with horrific serial killers? That's Criminal Minds. X-Files with witty ensemble banter and, uh, the Navy? That's the NCIS franchise. X-Files with Sherlock Holmes? That's Elementary.

And in Person of Interest, CBS has inadvertently created X-Files with science fiction elements all over again, only instead of alien conspiracies and the disorder of the post-Cold War landscape, the series is all about our uneasy relationship with the technology that surrounds us. What might happen, it asks, if artificial intelligence was already out there, manipulating power players behind the scenes to do its bidding? What if humanity were just an extension of its machines?

In the hands of creator Jonathan Nolan and co-showrunner Greg Plageman, Person of Interest has become a warped reflection of our real world. Where The X-Files metaphorically took stock of all of the horrible things that had been done in the name of winning the Cold War, Person of Interest turns a similar eye to the War on Terror. Its central Machine — a computer that can more or less predict the future — is an unholy amalgamation of NSA spying programs and the fact that Target might know you're having a baby before you do. Its main villain, a rival AI named Samaritan, plays like an evolution of the security state in 10 to 20 years.

The show is also, like X-Files, thrillingly inventive, going out of its way to try new things and stretch its episodic template as far as it can go. It doesn't always work — a season two episode that turned Harold Finch (Michael Emerson) into a high school teacher was kind of a mess. But when it does, it results in episodes like the thriller "Relevance," one of the most exciting, propulsive episodes in television history, or the fantastic "If-Then-Else," in which the Machine works through multiple potential timelines to decide upon the best one.

How I learned to stop worrying and love The Machine

Over its four seasons, Person of Interest has slowly but surely built a mythology around its central Machine. The series blows up its central conceit as often as it possibly can, to reveal newer, bigger depths in its mythology. In that respect, it's a much more disciplined show than The X-Files, which only returned to its ongoing alien colonization storyline for a handful of episodes each season and very quickly ran out of anywhere to go with it.

But Person of Interest has a couple of decades of TV serialization post-X-Files to draw upon, time that has been spent in figuring out how best to unspool these stories so they can keep going and going and going.

Throughout season four, the series has placed all of its pieces onto the board, just to remind you of how sprawling the show's story has become. The characters vie for independence — perhaps going analog in a digital world — but they are forever trapped by forces beyond their control.

All of that reminds me of The X-Files as well. But what does, more than anything else, is how both series are ultimately about control, about the idea that you might think you're in charge of your life, but you're being moved around by forces you can't possibly imagine.

Most of us try to pretend we don't know that, but the characters on these two shows are reminded of that constantly at every moment — and whether it's aliens or artificial super-intelligences taking control of them, the question is always whether that knowledge is blessing or curse.

Person of Interest airs Tuesdays on CBS at 10 p.m. Eastern.