MYSTIC, Conn. — Eleven acres of emerald jut into Fishers Island Sound, where sunlight dances like so many well-cut diamonds on gray, wind-whipped water, and the causeway that leads to this place — Enders Island — is just a football field long.

But for the young men who cross that tiny one-lane bridge, for the teens and young adults whose lives have been wrecked by drugs and alcohol, who have left behind a trail of betrayal and defeat, of hopelessness and paralyzing fear, it is nothing less than the passage of a lifetime.

And when they get to the other side, there’s a priest from Quincy, Mass. — a genial guy whose spiritual home as a kid was a triple-decker in South Boston — waiting for them.

He has the simplest of questions. It’s a life-changing one.

“Have you had enough?’’ the Rev. Tom Hoar asks.

It’s a question he had to confront a long time ago. Now it’s a question that he helps others answer — step by step, day by day.

“I’m grateful for God’s blessings in my life and in the life of the folks who come across that causeway,’’ Hoar said last week. “Because people who come across that causeway are looking for hope.’’

Hope. It’s been Tom Hoar’s stock-in-trade — the central part of his priestly life — for nearly 40 years now.

“There’s a slogan in the program that says, ‘To keep it, you’ve got to give it away,’ ’’ said Patrick Lynch, a former executive recruiter from Ridgefield who met Hoar in the early 1970s when they were students at Saint Michael’s College in Colchester, Vt. “He’s somebody who gives it away because he’s got it. He feels compelled to share the way he did it with other people to prevent the carnage.’’

That carnage is everywhere you look. The opioid epidemic rages on. The insidiousness of alcohol addiction destroys lives, careers, marriages, families, and futures.

Tom Hoar, president of St. Edmund’s Retreat, is devoting his life to charting a course for those who have lost their way. He knows. He was there once.

Hoar, 66, was the fourth of five children, whose mother went to work after his father, an MBTA mechanic for 42 years, developed cancer of the larynx. They lived in the close-knit Germantown section of Quincy, a peninsula of blue-collar veterans who had returned home from the war to contribute to the demographic colossus that became known as the baby boom.

“A great neighborhood,’’ Hoar said. “We all had to be home by the time Mrs. Murphy, a mother of nine, rang the bell for supper.’’

After Mass at St. Boniface on Christmas, Thanksgiving, and Easter, the extended family would gather at his grandparents’ home, that triple-decker at the intersection of L Street and Columbia Road in South Boston.

As a kid, he was an altar boy and active in the CYO, once expressing early interest in the priesthood. His mother had a tart response: “Get that foolish notion out of your head,’’ she told young Tommy Hoar. “I’m not going to support you for the rest of your life.’’

He didn’t listen. He went to Saint Michael’s, abandoning his pursuit of a medical degree, and ultimately collected enough academic degrees to put most people’s walls of fame to shame. Two doctorates. Multiple master’s degrees. On May 13, 1978, he was ordained into the priesthood.

And he felt empty.

“I never felt good enough,’’ he said. “Never felt smart enough. My brother was always the better athlete. Even though I excelled in school, internally I never felt good enough. And you see that in many alcoholics and addicts. I could preach a great sermon on how much God loved you. I wasn’t always sure that he loved me. Even though I achieved, I lived in fear.’’

And he developed a taste for alcohol. Good wine. Top-shelf whiskey. Fine cognac.

In early October 1989, he was leading a new campus ministry at his alma mater in Vermont. He was alone, drinking in his room when a fire broke out about a mile away. He was the fire department chaplain, so he answered the alarm.

“I went to this fire and the dean of students said to me, ‘Have you been drinking?’ And I said: ‘No, no, no, no.’ And the fire chief, who was a dear friend of mine said, ‘Have you been drinking?’ And I said, ‘No. I went out to dinner and had some drinks.’ ’’

He left the fire scene, navigating a sea of flashing red and blue lights. A mile later, he was back at home, where he looked in the mirror and took stock. “I said, ‘What the [expletive] are you doing?’ And that was my last drink.’’

Those who arrive here at Enders Island to hear that story typically stay for three to 12 months of post-treatment recovery. They develop personal and social skills. They sketch educational goals. These college-age men receive counseling, and more than 70 percent — a remarkable figure — are leading productive lives in sobriety.

“Most of them have either been kicked out of school, or fallen out, or failed to launch,’’ Hoar said. “Addiction closes people’s view of the world. They become isolated. So I take them to symphonies, museums, shows. They do volunteer work. Some take music lessons. Some take judo lessons, golf lessons, horseback riding lessons.’’

Simply put: Here, they re-start their lives free from substance abuse’s shackles.

And very few can afford the program’s $10,000-a-month price tag. But that’s OK. Somehow they make it work.

“He doesn’t know how to say ‘no’ to people,’’ said Claire St. Clair, the program’s finance manager. “He’s quite literally there for anybody. It’s always a struggle financially. We live hand-to-mouth. I’ll go to him chewing my fingernails and he’ll say, ‘By God’s grace we’ll make it.’ ’’

His board of trustees have told him that hope is not a business plan.

“But it works,’’ he said. “We say, ‘Give us this day our daily bread.’ And He’s done it.’’

Just before he went to college, Tom Hoar was the recipient of generosity that perhaps propels his blend of spiritual giving today.

His godfather, a senior MBTA executive, helped his family out when Hoar’s father got sick and helped pay for his college tuition.

“I said to him, ‘Billy, how will I ever pay you back?’ And he said, ‘Help another kid.’ I’ve always had that in the back of my mind.’’

And so when kids with addiction problems started traveling over that causeway, Hoar invited one to stay. Then two. Then three. And now up to a dozen at any one time. They are men today who testify that Hoar’s obedience to his godfather’s wishes has saved their lives.

One of them is Matt Gregoire, a 26-year-old who grew up in Jamestown, R.I., and nearly lost his life to pills and alcohol. When he was 22 and most of his friends were graduating from college, he was sitting on a bench downtown, sipping on a 40-ounce bottle of alcohol.

“My mom would find me on the ground after I had a seizure and would call the ambulance to pick me up,’’ he said. “She was just desperate. She was broken from it all.’’

So was he. Until he found his way to Enders Island. And to Tom Hoar.

Gregoire’s last drink was June 27, 2013. He got married in January. Next month, he will receive his nursing degree from Texas Tech University.

“When we got toward the Christmas season, I was going to candlelight Mass and I started to see and I realized there’s a place for me in this world aside from drinking a 40-ounce on a bench. It made me so honored to have someone like Father Hoar believe in me.

“Words can’t describe what a blessing it is to have him in my life,’’ Gregoire said. “It’s like a miracle.’’

A miracle. Like the small, life-changing ones that happen every day on this small island that sits next to a spectacular sea.

Thomas Farragher is a Globe columnist. He can be reached at thomas.farragher@globe.com.