I agree with #691. It does seem like the obvious answer is that Jack runs in to get the dog, but I’ll be disappointed if that’s the case. It just seems a bit too on the nose. I’m sure if that is what happens, it’s going to be done beautifully and I’ll cry and love it, but given how the show plays with and teases the viewers, I think they can do better than that.
I’m also still not sure that Jack dies in the fire.
But, I don’t think Jack would go back in after the dog. It’s very plausible that Kate went back in for the dog and that Jack went back in for Kate.
The Titanic references could’ve been foreshadowing!!! Jack sacrifices himself for Kate! I’ll never let go!
Just watched - so insanely sweet and insanely sad. Kate and Toby and the dog. <3 The joke about Jacob Tremblay!
I’m just going to add one thought to all of the above…
The scene with Kevin and Randall at the apt house where Randall is talking about getting old and death and all that…the way he talked about that all - and Jack - almost inferring (or maybe I was reading into it) that Jack’s death was untimely - but not necessarily because of an accident…but because of health…could it be that Jack survives the fire but somehow has a heart attack or something when they are all out of the house?? And maybe that is why his belongings in the ziplock bag are not burnt? Something happens and he is carted off to the hospital where he dies because of something secondary???
Also, was this mentioned above??
We now know that Randall/Beth working together on this apt building is mimicking what Jack/Rebecca planned to do - partner for building flipping.
Kevin seems never to have set things right with his dad. If the devastating fire had not resulted in anyone’s death, it seems like even Kevin would naturally have made a big effort to make up with his dad and would not feel deep guilt/regret in addition to loss.
OTOH, if Jack did die in (or because of) the fire, I found myself wondering whether Rebecca would have felt guilty, perhaps remembering that she had left the crockpot on and not knowing Jack turned it off.
I have an aunt who was a huge family photo/album person. She lost everything in a fire (no injuries or death, thank goodness). As I watched the scenes of the photos, videos, etc. burning, I thought of her. I also thought of how hard it would be to lose a father, a husband, and not even have the family photos and mementos.
I love this show!
I was picturing that literally the family escapes the fire, including Jack and are out on the lawn watching the house burn down and Jack has a heart attack right there or smoke inhalation or something - and is rushed to the hospital - but Kevin doesn’t get the chance to see Jack - because he and Sophie are off in some party in the woods (remember he said that to her??)
And of course Jack, being Jack decided to clean up the freakin kitchen before he went back to bed. From putting the food away, to sweeping the floor - to turning off the crockpot. 
Depending on what happens in terms of the fire and getting out of the house, with a cast Kevin may not have gotten out of the house had he been there. To a degree, he may have benefited selfishly with not being involved with the fire which resulted from the fight he had with his parents.
If Jack dies of a heart attack or smoke inhalation, why would Kate feel his death was her fault?
^^^He may have went in an extra time for the pet - and that trip in may have triggered a medical problem.
I’m grasping at straws!!!
I do not remember what all was in the bag of belongings. If the things belonged to Jack, I don’t think he would have had them with him; wasn’t he undressed for bed? He would have had his watch, ring and wallet on his dresser or somewhere, and I would assume those might have been destroyed; I don’t think he would have grabbed his wallet while trying to get his family out of a fire.
Might the belongings be Kevin’s? Maybe while out at the party he was arrested for underaged drinking, and the bag was his. Jack then dies sometime after of a heart attack or a car wreck. OK, I am not a tv writer, nor do I play one on tv! :))
Wow. You’re observant! Were you a literature major?
Ahh, the great Kate Burton, daughter of theatre royalty, Richard and Sybil! She’s terrific.
I don’t have any guesses as to what happens to Jack. They have practically shoved the fire clues down our collective throats so if it has nothing to do with the fire, that will just be ridiculously weak.
On another note, I really love the girl who plays teenage Kate.
And Kate Burton’s daughter is Charlotte Ritchie, Barbara on Call the Midwife.
When I think about it, I don’t “love” any of the kids as teenagers - is that how it’s suppose to be?! 
Kevin of course is kind of mouthy and acts above the rest of the family. Even him and Kate don’t seem super close(?)
Kate is so moody!
Randall - less not to like but he seems sort of easy to influence - book smart but maybe not socially smart - awkward with girlfriend (though many teen boys are), awkward when he went on the college visits.
Just interesting because I LOVE all three as young children and then as adults (Kate the least though for me).
Also, haha that Kate thought Toby was looking at porn and it was instead, “P” for puppies!! Petfinder will get you EVERYTIME if you look there!!!
@abasket I agree with you about the kids as teens. When I mentioned the teenaged Kate, I meant that I loved the actor and her portrayal. Her acting skills are subtle and precise. But then aren’t all teens unlikeable at moments? 
I actually don’t fall into that camp of thinking teens aren’t “likeable” - just never have. My own three were easy (happily). But if I really think about these three…I can see how tough it is for Rebecca and Jack both who seem to want so much to have what they had when the kids were little.
My girls as teens were easy overall, too, although they had their moments when they weren’t always likeable. My comment was mostly a joke, hence the smiley.
I just read a new theory about the fire. Kind of intriguing. http://www.cosmopolitan.com/entertainment/tv/a15871250/this-is-us-jack-death-dog-kevin/?src=socialflowTW
^^ Agree! Really interesting theory!
^^Yes!!