Ted (Josh Radnor, left) asks The Mother (Cristin Milioti, right) to marry him. She said yes. And then she dies?? (CBS)

For a while, a certain underground conspiracy theory among “How I Met Your Mother” fans has been gaining steam but it was something nobody really talked about out loud. After all, it was a ridiculous idea. The producers would never do that. It’s not even anything that could be taken seriously … right?

Then, on this week’s episode, it was hinted at: the Mother has been DEAD THE ENTIRE TIME.

At first, we weren’t sure what to think because it seemed to be one of those classic “HIMYM” tricks designed to make viewers crazy. The producers have always loved a good red herring, or a way to throw the audience into a frenzy guessing what might happen. In the many years leading up to revealing the Mother’s identity (which finally happened in the Season 8 finale; it was Cristin Milioti, playing a still-nameless woman), all the hints we were given — yellow umbrella, Rachel Bilson’s roommate — wound up being completely useless because it was someone the audience had never seen before.

Now, “The Mother Is Dead” theory appears to not only be picking up traction, but seems to be a distinct possibility. At the end of Monday’s episode, with just four to go before the series finale on March 31, Ted (Josh Radnor) and the Mother are shown sometime in the future spending a romantic weekend at the inn where they first meet. There’s already a pall cast early on the conversation when the Mother tells Ted, in all seriousness, “I don’t want you to be the guy who lives in his stories. I want you to move forward.”

The “HIMYM” writers love twists. Remember when Ted and Robin were a thing? (Karen Neal/Fox Television)

However, the whole show has been Ted telling one story after another in each episode, so that’s unfortunate already — if she’s dead, Ted has disobeyed her for nine seasons. That’s not the most compelling evidence, though: At the very end of Monday’s episode, after Ted has told a story (because that’s what he does!) about Robin’s mother unexpectedly showing up to her wedding, the Mother scoffs: “I mean, come on, of course she showed up,” she says. “What mother is going to miss her daughter’s wedding?”

All of a sudden, Ted looks like he’s about to burst into tears, and he puts his head down. The Mother realizes this. “Oh hey, no … come on,” she comforts him.

“It’s okay, I’m fine. I’m okay,” Ted weeps. The Mother then starts welling up too, before quickly changing the subject to something more cheerful. End scene.

Hmmm. What to make of this? In a normal show, it would appear that the Mother will not make it to her daughter’s wedding, because she’s dying or about to die. Again, this is “How I Met Your Mother”: It’s possible that, who knows, there’s a trip to space planned that might conflict with the daughter’s wedding date? Is this mysterious future scene before Ted and the Mother have kids and they think they might not be able to get pregnant and have a daughter? The trick with “HIMYM” is to think about the weirdest thing that could possibly happen and work your way back from there, and you’ll still never figure out what the producers have up their sleeve.

Really, this could all be a big, misleading twist. Just for fun, though, can we just step back and imagine what the Internet will do if it reveals that after nine seasons of Ted telling the tale of How He Met Their Mother to his future kids, it’s all because the mom is dead? It would be a triumph for conspiracy theorists everywhere, but Internet commenting systems might actually explode. If there’s one thing you don’t want to do, it’s make an obsessed fandom feel like they’ve wasted their time (still thinking of you, “Lost”) — and that’s how many would feel if the producers revealed that the end of a glorious love story is actually a completely depressing tale of death.

Anyway, for the initial question: Is “How I Met Your Mother” really going to kill off the Mother? Being accustomed to classic producer/writer trickery, we’re going to venture “no.” Still, after that abominable “Dexter” series finale still fresh in our minds, we no longer have total faith that TV writers always know what will make for a satisfying ending to a long-running show.

The happy (?) couple, before they meet. (Ron P. Jaffe/Fox © 2013 Fox Television)