'How I Met Your Mother' Season 9 Spoilers: Ted Has Alzheimer's; Mother Still Alive?

Fans of "How I Met Your Mother" has for long wondered the reason behind Ted narrating to his children the story of how he met their mother. And now, like Ted's children, fans of the show also would not have to wait for long to find out the reason as the show is airing its final episode on 31 March.

But that has not stopped people from speculating how the story might end, and one theory floating around suggests that Ted might be suffering from Alzheimer's. This might be why he wants to narrate his memories before they fade away.

This has put to rest the mother-is-going-to-die theory, which gained momentum soon after the "Vesuvius" episode aired. The episode had Ted crying when Milioti's character asks "what mother wouldn't attend her daughter's wedding?" and fans were quick to draw conclusions that the mother wouldn't be alive when their daughter walks down the aisle.

But now, it looks like Ted is the one who would miss their daughter's wedding, if not physically, then mentally. In the "Vesuvius" episode, although the mother asks Ted to stop living in the past, she lets him recount his good days with his friends, probably because she knows he won't have anything good to look forward to in future.

Supporting the theory, a Reddit user stated: "The entire show is about Ted looking back on his life, looking at all the good and the bad parts. Was he right to do this? Was he a good person when...?

"That's not normal for someone who think's they're going to lose their soul mate, that's what someone does when they think they don't have a future."

Also, it looks like Ted's children do not know about his ailment as they would not be giving him annoying looks if they knew he had Alzheimer's.

Their "hurry up, dad" look has also put a stop to speculations of the mother being dead, as no one would show annoyance when their dad is regaling stories about their dead mother.

However, these theories might still be wrong, according to Pamela Fryman, director of the series.

"People are so sure and they have such an opinion about what they think is going to happen, but nobody is 100 percent right," she was quoted as saying by TV Guide. "I think people will be happy with the way this plays out. It's a great ending."

The finale episode of "How I Met Your Mother" is titled "Last Forever" and it will air on 31 March.