At the Sausage Factory, the three dogs were lying on a container belt

Max: Your know what? I mean, this may be the sausage talking, but your Okey, Duke.

Duke: Right back at ya, man. You know when I met you, I was all like, "I don't know if I like him" But now that I know you, I'm like, "I like him." You know, I saw this place from the outside many times. Had I know what treasures awaited within these walls, I would've broke down that door a long time ago, I'll tell ya!

Max: Yeah, what are you talking about?

Stella: You mean that you've been to this place before?

Duke: My old owner and I used to live around here.

Max: Duke, man, wait. Did you used to have an owner?

Duke: Well, It was a... was a long time ago. I don't want to talk about it.

Max: Yes, you do. Come on.

Stella: Max...maybe you shouldn't force him into taking it.

Duke: Well, I don't know. But you know what? He was so cool.

Max: Yeah?

Duke: Yeah. He was the best.

Flashback

In the flashback we can see Duke as a puppy looking out the glass pen in a pet store, playing with other puppies until an elderly man enters the store and adopts him.

Duke: *narrating* Man, we had fun. We played fetch. We'd go for walks. We's take naps. We were both but mappers.

Time pases as they sleep together in a chair, we can se Duke growing larger and larger. When he was full grown, the two of them sit in a porch with his owner while watching the sunset behind the Brooklyn Bridge.

End of flashback

Duke: I got out one night, chasing a butterfly of a car. By the time I had caught up with it and ate it...

Max: Probably a butterfly, then.

Duke:...I realized I was so far away from my home, I couldn't find it. Few days later, I was picked up by Animal Control. *sighs* I had a great thing going. But I had to go and mess it up.

Stella felt bad about Duke, then she started to hear voices in her head about the time someone special left her, that made her feel even worse. So she walks up to Duke and comfort him.

Stella: Hey, you didn't mess anything up. You were just having fun. You couldn't have known that would have happen. But right now there is no need to regret what you did in the past, that already happened. I mean, look around you. You have a new life, new owner, you should be proud about that. And you know what, are a very lucky dog. Remember that.

Duke, touched by the her speech, started to nuzzle her. Stella was at shock at first, I mean she already did the same to him back at the river, but this one was not an accident. It actually felt nice, so she nuzzled him back

Duke: Thanks Stella.

Stella: No prob.

Suddenly Max came up with something.

Max: Duke, we got to go to your house!

Duke: Nah

Max: You know, your owner's gonna be relieved.

Stella was not very convinced about Max's idea. Although, Duke clearly misses his owner, so she thought maybe... maybe they should reunite them...for them to see each other again.

Duke: Will he?

Max: Yeah!

Stella: If he loved you and by the way you talk about him, it sounds like he really cares for you.

Duke But he never came for me. Maybe he...Maybe he didn't like me.

Max: Hey, of course he liked you, he was your owner. I mean, he's probably worried sick.

Duke: I don't know.

Max: Well, I do know and we're going. Your owner's gonna freak. I'm freaking out just thinking about it.

Duke thought about it and he decided to go to his old house and see his owner once again

Duke: Okey. Let's do it.

Animal Control 1: There they are!

Stella, Duke, Max: *gasp*

The animal control arrives

Animal Control 1: All right doggy, come on.

Stella: Let's get out of here!

The trio flee from the animal control.

Animal Control 1: Where do you think you're going?

Animal Control 2: Come back here, you dogs!

Duke knocks a stack of boxes onto the dog catchers.

To be continued.

For this chapter I took some inspiration on a "Secret Life of Pets" fanfic I read a few months ago written by @shontobears545653 which was pretty good, I highly recommend you reading it.