We now know the real culprit in Jack's death. The smoke detector. Dun-dun-DUN. Or at least we think we know...

"This Is Us" Season 2, Episode 12, "Clooney," revealed that Rebecca and Jack forgot to get batteries on their trip to the mall. That mundane task turned ominous when the cameras showed the smoke alarm without batteries. We know the house eventually burns down. We know Jack dies. So there's another clue.

Did we also get more clues as to why Kate blames herself for her dad's death? There are still several theories on that. Based on this week's episode, some fans think Kate will blame herself because she distracted her mom from getting batteries at the mall. But that sounds like a stretch. Rebecca had asked Jack to remind her, it was on both of them, and Jack was distracted too.

Is it possible that Kate, no longer resigned to eating carrot sticks, decided to cook some food and that started a fire? Maybe. But previous fire hints suggested there were already electrical issues, causing outages in the house.

Some fans think Kate feels guilty because Jack saves the Pearson family dog in the fire. We keep seeing Kate with the dog, like he's her dog. Perhaps when fire breaks out she asks about the dog, and Jack goes back to save him? That's one running theory at the moment. It's not a new theory but it's picking up steam.

There are other theories, and it's possible the dog was a red herring to throw us on the wrong trail. Kate is not the only one who feels guilty after Jack's death, and there are multiple reasons to be revealed. No matter how Jack dies, we saw how he lived, and losing him will be heartbreaking for fans.

"This Is Us" airs Tuesdays at 9 p.m. on NBC.

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