The job description was for a security guard in a place where few wanted to work: McPherson Square Library in Kensington.

But Sterling Davis, a product of the King’s Plaza Housing Development — another rough place in a rough South Philadelphia neighborhood — knew it would be an honest dollar. And Sterling would go to the moon for an honest dollar.

“I’ll take that challenge,” he said.

And soon after he put on his blue uniform shirt, he adopted a credo to work by: Once you’re inside this library, you’re safe.

That extended to everyone. To the kids for whom McPherson — which would become the heart of Philadelphia’s opioid crisis, but even then was pockmarked with needles — was their only refuge. To teenagers who thought no one was in their corner. To the adults who carried themselves in such a way that showed Sterling they were hurting.

Outside, drugs were all over the place. And there was no playground, no lights, no outlets for any of the kids at the library. The kids who would test Sterling and try him, who didn’t trust him, whom he assured: “I’m not going anywhere. I’m staying. I’m staying.”

And stay he did.

Sterling, who is married to a crossing guard and has five grown children — two still in college — stayed as the community built a new playground and launched new programming. Along the way, he began to see his job as something more than being a security guard.

He is 54, with a stocky frame, calm presence, and soft voice. He learned that calm from his dad, a factory worker who ran the local community center, and his mother, a preschool teacher.

He learned compassion, too. Two of his cousins were lost to drug addiction.

“When I first started [at the library], it was just doing a job,” he said. “And then as I got used to doing the job, and seeing how some of the people were suffering, and didn’t seem like they had anybody out here that cared, I began to show a little bit of empathy and sympathy.”

He joined community groups, started attending the meetings in the basement of the library — even if he was just a quiet figure at the back of the room. He learned how to use the library’s book of resources for residents: job training, child-care needs, housing, GED classes, resumè writing. The kids no longer tested him.

“He makes sure it’s safe,” said 11-year-old Ian, a John B. Stetson Middle School student who visits the library to use the laptops. “He doesn’t let no fighting. He doesn’t let no cursing. All he wants is respect in this library.”

Sometimes Sterling just talked patrons through paying their fines. He could see past the yelling, because he knew they weren’t really angry about the fine. It was about all the reasons why they couldn’t pay it.

Then, last summer, the storm descended.

The lawn outside Sterling’s library filled with crowds of young people from all over, who came to Kensington for the heroin, and to his lawn for a safe place. And Sterling had to take his credo outside his library.

And he did.

The librarians trained to use Narcan, the overdose-reversing drug, as scores of people began to overdose around the branch. Sterling kept watch from the front steps for when they fell.

“He was the anchor that kept us going,” said librarian Chera Kowalski, who saved six people on the lawn that summer. “He made sure I was safe. He made sure the people were safe. He had no stigma against doing it.”

When the storm on the lawn quelled, and some of the librarians moved on, Sterling knew he had a new job: saving lives.

And he has.

He’s reversed six overdoses. I’ve seen him save two lives myself. He is calm in the storm.

“I just go help them, walk away and make a report,” he said. “And say I just helped another person survive another day.”

Sterling’s job description is expanding again. Last week, he received training in youth and adult counseling. He’s using new techniques to get the kids in the library — and the people on the lawn — to open up.

“How’s your mood today?” the security guard now asks people. “Do you feel like talking about it?”

He does what the best of us do at the heart of a crisis where there’s so much tension between neighbors and people with addiction. Like the librarians did before him, he engages.

“He gets it,” Kowalski said. “He gets what’s going on in the community. He’s willing to engage with it. He’s putting himself into it.”

He has kept his library safe.