[Screaming] Oh my god
[Kimmy] And I'm like Frank, are you okay?
He says, Kimmy he says we were thrown to the floor out of our chairs.
He says I'm trapped on the 87th floor.
He says it's getting difficult to breathe
and he says you need to promise me
everyday for the rest of their lives
that you tell Zoe and Garrett how much I love them.
It didn't register at the time, you know that he was saying goodbye.
And then he hung up and that was at 9:22 a.m.
[Ron] It was a beautiful day.
There was a big loud explosion
and then as I was leaving the trading floor
the plane hit our building.
The right wing sliced right through our trading room.
I got knocked flying, debris came down on us
and then we went into the stairwell.
Why did I survive when so many of my colleagues didn't?
How did I get out when they didn't?
[Reporter] For Kimmy Chedel and Ron DiFrancesco
9/11 is not only burned in their mind's eye
it's seared in their souls.
They can't forget where they were then
but 20 years later, we also wanted to know where they are now.
Every time I think about it
it brings me back into the building
the tower, the stairwell and what went on.
[Reporter] Ron is said to be the last known survivor
of the World Trade Center attack.
He escaped through a burning stairwell.
It's still a hard story to tell.
The smoke was getting pretty thick and heavy
people were starting to
drift off and go to sleep.
And that's when I heard a voice
call me and it was a calm, clear voice
and told me to come this way.
So I went towards the thickest smoke and the fire
and I pulled back a sheet of drywall to reveal the staircase below.
I slid down there and then
ran through three flights of stairs that were on fire.
Then I ran down.
What was that voice?
So some say maybe God or an angel
and some say it may just be me
you know my adrenaline
but it was a clear, calm voice.
[Reporter] Ron doesn't know how he got out.
He ended up in hospital
a gash on his head, a broken bone in his back
and burns to most of his body.
His contact lenses had melted to his eyes.
His wife Mary was shocked when she saw him.
[Mary] I wasn't sure he was going to survive
and I felt incredibly grateful that he was alive, that he got out of the towers
and I promised myself then that I would try to be worthy of the gift of his life.
[Reporter] It would take months to get on his feet.
Ron and his family moved back home to Toronto
and while life moved on
Ron says he couldn't.
[Ron] Mary took the brunt of everything.
She took care of the kids, took care of the house, took care of the family.
I was blank for a long while, right?
I just, I didn't care about anything.
I didn't want to hear noises I just -- I was void of life I guess.
I was just existing.
What was that like for you Mary?
Physically he recovered
but emotionally he sort of disappeared and the kids noticed and they
you know, wondered why he was angry
wondered why he was sad
and it wasn't enough to survive, you know
we had to learn to thrive again.
And that was tough.
[Reporter] Focusing on charity work
and speaking about mental health has helped.
Everybody struggles with their mental health at some point in time
and what can we do to help make it better for people, for ourselves
and so if I talk about it I feel a bit better after I do a talk.
What's in all these binders?
So these are all cards.
[Reporter] And there has been so much support over the years.
Binders bulging with notes of well wishes
and tucked away
Ron's watch, still encased in dust.
It stopped at 9:59 a.m.
the moment the south tower came down.
They're just important reminders of how close we came
and how near death Ron was.
[Reporter] But Ron says he still walks a fine line
between gratitude and guilt.
I left a lot of colleagues there
right in the stairwell
so I'll carry that with me forever.
Is it a miracle, is it luck
am I blessed, I don't know.
What do you think?
I'm blessed, I got 20 more years of life right?
And if I get one more day it's a bonus, so.
[Reporter] Frank Doyle wasn't as lucky.
[Kimmy] He was just a really special, unique person.
Very loving, very funny, crazy about the kids.
[Reporter] Frank worked on the 87th floor of the south tower.
When I first met his wife Kimmy Chedel at ground zero
she was clinging to the hope that he was still alive.
I just feel like I gotta find him and I gotta bring him home
one way or another.
In my heart, I thought you know
maybe he came down with the building, maybe they found him
maybe he can't remember you know who he was
maybe he didn't have his wallet on him.
It was just so devastating.
It was like in my mind I was trying to convince myself
he's gonna come home
he has to come home.
Because you, you were two years old.
You can't have many memories or do you have any?
I have a few memories with my dad.
Not sure if they're real memories but it doesn't matter now.
Just the fact that I feel like I did know him
and I remember some things.
[Reporter] Kimmy was determined to keep her husband's memory alive for her kids.
She left their home in the U.S. and moved back to Quebec
to start what would become a lifelong mission.
I think how did this, you know, little girl from Sainte-Marguerite, Quebec
end up in New York City
falls in love with an American and he dies in a terrorist attack like
I still sometimes kind of take a step back and think
like this is -- is this actually our story?
And now my focus has really been Frank's legacy
and you know what we can do
and what we can create in terms of change
and to give back and to live our lives
you know in a positive way
and try to make something positive out of this.
[Reporter] Frank was an avid athlete
so friends and family gather to hold triathlons in his name every summer.
In the last few years
the focus shifted to building preschools in South Africa in his memory.
With the help of her children
including Zoe.
When I think about my dad
I don't think about 9/11 and the tragedy and everything and I think
it's because of this team and the support system that we were raised with
and how she decided to raise us
and be strong for us
and always be so positive that we're lucky in many ways.
[Reporter] Twenty years is a long time.
Kimmy found love again, but in another devastating blow
lost her partner François two years ago to cancer.
Kimmy says Africa
the inspiration behind it has saved her.
This is from June of 2018.
[Reporter] Wow, amazing.
But in each of these tragedies
I realized that when I go to Africa soon after
I feel like I'm going to be okay.
When I go on these trips
it's like I heal faster
I feel like I have a purpose
I'm happier.
I don't know how you do it but it's been
incredible to see how far we've come.
[Reporter] 9/11.
It made fragments of their lives
but they're still finding light through the pieces that will always be missing.
Ioanna Roumeliotis, CBC News, Toronto.