Islander Earl Johnson recounts his escape from the towers in a new book.

“Bearing witness” is how Earl Johnson honors those whose lives were fractured or lost in the 2001 terrorist attacks on the World Trade Center.

Johnson, a former Wall Street banking and brokerage professional, was working on the 51st floor of the North Tower when the first plane hit.

As he descended the stairs to safety, he passed first responders on the way up. The happiness he felt seeing them and, later, the impact of their bravery sent him on a life-changing course.

“People want to know more in-depth what it was like that day, what I call ‘the Exodus,’” said Johnson, a Bainbridge fire commissioner who speaks to groups about his experience. “That opens the door for sharing with people the witness part that I saw that day.”

Nearly four years after the attacks, Johnson recounts his experience, and the effects it had on his family, in “Stairwell to Heaven: A 9-11 World Trade Center Survivor’s Story.” Johnson and his wife, Arlene, will discuss their experience at 7:30 p.m. on Feb. 16 at Eagle Harbor Books.

Johnson calls his writing “part memoir, part memorial to the fallen.” Arlene Johnson adds the view from the other side – that of a family wondering if they’ll see their loved one alive.

After he exited the tower, Johnson gave thanks and made the long trek home to Freehold, N.J., where his wife and three children had joined him from Bainbridge barely a month before.

Two weeks after 9/11, Johnson accepted a Bainbridge job offer and the family happily returned to the island.

He came back, he believes, a different man. Having embraced the life changes the catastrophic experience brought him, he sought and won his fire commissioner position and began speaking to groups about what he and his family went through.

Finding that “hugely rewarding and very valuable,” he retired from Wall Street last fall to become a professional speaker.

“Everybody has (9/11) as a marker, where they were, what they were doing, and they want to talk about it,” Johnson said. “It just shows how deep a scar that is.”

Before moving back to Bainbridge, Johnson took advantage of the counseling offered by his New York company. It helped “probably more than I can say.”

Johnson looks forward to describing his 9/11 experience and answering questions.

Children make the best audience. When he talks about police officers, firefighters and military people, “the kids just light up,” he said.

“It’s important for them to know what strangers can do for one another,” he said. “We all have that within us.”

Before he reached a level of peace, Johnson admits he did ask, “Why me?”

“I spent nearly 30 years in the Wall Street world, never working in New York before that two-week period,” Johnson said. “I was supposed to be there.”