The dog now known as Suzyn Pupman was cold and alone about 3 a.m. Saturday, looking to escape the rain, when she saw an open door, and followed the heat up the steps and inside the Fishtown home.

Upstairs, Jack and Emily Jokinen, both 34, and their 1-month-old daughter, Johanna, were asleep. About an hour later, Emily opened the bedroom door and saw on the stairs the injured and malnourished stray with a limp.

The dog would get the love she didn’t seem to have had. But first, the couple were determined to figure out what had led the scared but adorable canine to their home.

Jack Jokinen said in a video posted on Twitter that he went downstairs and checked the front and back doors and the windows. They were locked.

“This mystery puppy in our house," he recalled thinking, "how did this happen?”

He posted about discovering the stray in a series of tweets that had garnered almost 30,000 likes as of Monday afternoon.

Next, he checked security footage and saw that after walking his other dog, Jorge Pawsada, who is known as George and is named after former Yankees catcher Jorge Posada, he hadn’t completely shut the door, and the wind blew it open. The video shows the stray approaching the Jokinen home about 3:15 a.m.

About 20 minutes later, a passerby noticed the open door and yelled to inquire if everything was OK, Jack said he learned from the security footage, and then closed the door.

“Of all the bad things that could happen when your front door is left open, to end up with a sweet dog who just needs a good home, I mean, wow,” Jack said in a video. “This could’ve gone a lot worse."

The family called animal control and then decided to take the dog to the vet to see if she had an identification chip. She didn’t. She did have damaged teeth, fleas, no vaccinations, and a pad missing on her feet, Jack tweeted.

He posted photos of her first day with him, including her curled up inside a cage after receiving medicine for fleas and getting a bath.

“Gotta lather her up and let her sit 5min to get all the dead fleas and ticks off,” he tweeted.

She’s 9 years old, Jack learned. The couple named her Suzyn Pupman, Suzy for short, after Yankees sportscaster Suzyn Waldman. (Jack is a self-described Yankees “super fan” who grew up in the Bronx and describes Yankee Stadium as his “favorite place on Earth.”)

He said he and his wife will give Suzy “a dignified end of her life.”

“This dog was in such bad shape. Whoever would’ve had it is a terrible person," he said in a video. "So we’ve decided to keep the dog.”

Suzy has quickly developed separation anxiety, he said, and is sad when left alone. She now sleeps along with her adoptive brother Jorge, in bed with her parents, snuggled between them toward the middle and foot.

She’s on a low-fat diet to gradually raise her weight from 19 pounds to the high 30s, Jack said. They aren’t sure exactly what kind of dog she is, but she looks like a mix of a terrier and lab.

The Jokinens are accepting money via Venmo for her medical costs — the likes of fleas, ticks, foot infections, dental work, and a heart murmur — but said the family would take care of the dog even without any donations. If they get more money than they need, he said, they will find a cause to donate to. So far, Jack said, they have received $15,000, and he believes Suzy’s story is bringing people together at a time when it seems to him people are always “looking for reasons to fight each other.”

He called her “the internet’s dog."

“It’s the holiday season," he said. “Isn’t everyone looking to find a little joy every day?"

In the days since Jack Jokinen posted about discovering this dog in his home, he has created an Instagram account for Suzy and has been featured on local television.

In one post, Suzy is shown watching a video on TV that shows her asleep on the floor. The caption reads:

“Two nights ago I slept on the street. Tonight I watched myself on TV from a bed. Thank you @emjjokinen, @jjfromthebronx and @jorge_pawsada