He doesn’t remember climbing the pale green fence that edges the Key Bridge. He doesn’t remember jumping or hitting the icy water below. It was, he told his father, almost as if he was in a trance, going through motions he was helpless to resist.

On that day in early February, the man felt he had to die. He might have been successful, too. But someone who was running along the Potomac that morning saw the man jump, grabbed a boat from the Key Bridge Boathouse — closed for the winter — and fished him from the water.

The Arlington County Fire Department responded and took the man to a hospital. Now his family is left wondering who the mystery good Samaritan was and how they can express their gratitude.

“Thanks to you, he has a renewed chance to live and we have a renewed chance to love him and help him find good treatment for his illness,” wrote the suicidal man’s father in an e-mail sent to The Washington Post.

I spoke with the man’s father. Because of the stigma associated with mental illness, I’m not printing his name or his son’s, but I want to share their story and invite the Samaritan to get in touch.

“I just want to look him in the face and thank him,” said the father. “For me, it’s a little bit of therapy. Is that the right word? I would like to hear the fellow’s story. Where it was in the river, what it involved and the whole nitty-gritty of it.”

He thinks he might find solace in the details.

It is not an easy thing to think about. The father said his son learned 10 years ago, when he was in his 20s, that he is bipolar. The son is prone to the manic energy that comes with that diagnosis but had never shown any likelihood of harming himself. He was seeing a therapist and taking his prescribed medication.

And then came the awful phone call from the police. The fall from the bridge fractured some bones in the son’s neck but not any close to his spine. He’s out of the hospital and back at his job. He’s on a new treatment regimen — increased therapy and new medication — which seems to have made a difference.

“You’d think: Doesn’t he know what this would do?” said the father. “This would devastate us for the rest of our lives.” But he points out that people such as his son aren’t capable of thinking clearly when gripped by mental illness.

“At that moment, you feel in so much pain, you can’t focus on how this would affect anybody else,” said the father.

Being touched so directly by mental illness has changed some of his viewpoints.

“I remember when they put up the big, tall fences on Duke Ellington Bridge,” said the father, referring to an anti-suicide measure installed in 1986. “I was probably one of the people who said it’s going to kind of destroy the appearance.”

Now he thinks that sort of barrier is a good thing to have.

I asked what people misunderstand about mental illness.

“That it’s an illness,” the father said. “It’s like any other illness, but there’s such a stigma. If you get cancer or gout or a cold or a broken bone, nobody thinks that this is something bad that you did. But that’s the way people feel about mental illness.”

His family has been helped by a local chapter of the National Alliance on Mental Illness.

“It’s been one of the greatest things for us to be at these meetings and meet people with different diagnoses,” he said.

If you were the person who had the presence of mind to paddle across the frigid Potomac and rescue a stranger, send an e-mail to me at john.kelly@washpost.com. I’ll put you in touch with the family of the man whose life you saved.

“There’s no way to repay saving somebody’s life,” the father said.

He’d at least like to say thank you.

For previous columns, visit washingtonpost.com/johnkelly.