MULTYFARNHAM, Ireland » The setting could hardly have been more incongruous. Outside the window, lush pastures spread in the perfection of a late winter morning. Inside, a small man with a yellow star pinned to his sweater captivated an audience with the horrors of his boyhood in the concentration camp called Bergen-Belsen.

The man, Tomi Reichental, described seeing his grandmother’s body being thrown onto a cart overloaded with other corpses. He was only 9 years old. By that age, he had already experienced arrest and beatings by the Gestapo; the glow of the crematories through the cracks of the cattle car that took him to Bergen-Belsen; the assault of the spotlights, the shouts and the dogs as his family was hauled from the train; the scavenging for food; and the sight and smell of the piles of decaying dead.

It is never easy to hold the attention of hundreds of teenagers, but for a couple of hours Reichental did with his compelling story. He will be 80 on June 26, and with his companion, Joyce, at his side, he drives around the country giving talks to schools twice a week. He is fully booked for the rest of 2015.

"People tell me I’m the fittest Holocaust survivor alive today," he said, smiling.

The pupils here at Wilson’s Hospital School were the latest to fall under his spell. Even the self-styled tough guys hung on every harrowing word.

For Reichental, it had started as bullying, with name calling at school, escalating to physical abuse and ending with Bergen-Belsen. His message to the students is simple: "If you see someone being victimized, don’t be a bystander – stand up. If you see someone being treated badly, get involved." Afterward, they gave him a standing ovation. Pupils and teachers then lined up to buy signed copies of his memoir, "I Was a Boy in Belsen."

"Take this chance to ask me anything you like," he told his young audience. "There are not so many of us left."

It was mid-October 1944 when he was rounded up by the Gestapo in a shop in Bratislava, now the capital of Slovakia. For nearly 60 years, he never spoke about his experiences in Bergen-Belsen. He never even told his wife of more than 40 years or their three sons. But after her death in 2003 and his retirement from the Dublin jewelry business he owned, he has hardly stopped talking about what happened.

There may be an impression of making up for lost time, although he does not see it that way. "I owe it to the victims that their memory is not forgotten," he said. "It’s not that I didn’t want to speak about it before. It’s just that I couldn’t. There are thousands like me; I believe it is nature’s way of allowing people to deal with things."

His first classroom appearance, made at the urging of one of his sons, did not go well. He broke down as he told his story; worried parents would complain. But as he continued and his audience grew, so did his demand. Now he travels like some old-fashioned preacher to tell his story, so younger generations will know what happened to him and to millions of others.

He still has trouble controlling his tears. "When I’m speaking, I’m reliving my past and occasionally the whole picture becomes so real, I can’t help but cry," he said. "Someone once suggested I leave out the part that upsets me, but so many aspects upset me I don’t know what the trigger will be from talk to talk."

He tells of how his idyllic village childhood was shattered when Slovakia became a puppet state of Germany, and in 1942 the regime began to deport its entire Jewish population, the vast majority of whom would perish in death camps.

A couple of weeks after he, his brother, mother and grandmother were finally captured by the Gestapo – after evading the Nazis for two years – they were forced into a cattle car on a freezing November day. He believes the train was diverted to Bergen-Belsen only because the Nazis had been forced to destroy the crematories in Auschwitz and Birkenau that very week ahead of a Soviet advance.

"It was sheer good fortune," he said. "A few days earlier, I wouldn’t be here now. Like so many others in my family, I would have surely been killed in Auschwitz."

His father was captured separately but escaped and joined local partisans. The family was reunited after the war, returned briefly to a country where they were no longer wanted and left in 1949 for Israel. In 1959, Reichental came to Dublin at the behest of a relative to start a small zipper factory.

He does not regard himself as vengeful. So in 2012, when an Irish woman living in Hamburg heard about his story and said her neighbor, a former Bergen-Belsen guard, would be willing to meet him, he went.

"As far as I am aware, it would have been the first private meeting between victim and perpetrator," Reichental said. "She would have had a lifetime to reflect. I could never forgive, but I could understand how a 21-year-old girl might end up being what she was, so I decided to see her."

Gerry Gregg, a filmmaker, learned of the intended encounter and decided to record it. "Close to Evil," which debuted here in September and had its United States premiere earlier this month at the Chicago Irish Film Festival, follows Reichental from his home in Dublin to Hamburg to meet the former guard, Hilde Michnia, now 93.

The would-be conciliation, however, took an unexpected twist. During their research into Michnia’s background, the filmmakers discovered a 2004 interview in which she was unapologetic for her role at the camp, where at least 52,000 people perished. Michnia then backed out of the film, Gregg said, because of an illness.

After spending a year in jail for beating two starving men senseless when they tried to take a couple of turnips from the camp’s kitchens, she was released in 1946. She married and had three children. In the 2004 interview, she insisted that only lazy prisoners went hungry. She said she spent her time working in the kitchens and saw no ill treatment and could not recall any smells from rotting corpses.

She described her role as a guard on an infamous forced march in 1945 from Gross-Rosen concentration camp in Poland, in which an estimated 1,400 women died of starvation and cold. She said she prepared stews and hot chocolate for the prisoners.

On Jan. 25, Gregg showed "Close to Evil" in L 5/8neburg, Germany, the city where Michnia was convicted after the war. After viewing it, a local historian, Hans-J 5/8rgen Brennecke, who had contributed to the documentary as the son of a Nazi war criminal, filed a complaint against the former Bergen-Belsen guard for her role in the forced march, for which she was never tried.

In early February, the local prosecutor’s office in Hamburg confirmed that it was investigating. In the end, Reichental never met his former captor, who told The Irish Times last month, when asked about the complaint: "Not Bergen-Belsen again. It’s 70 years ago. They should leave small fry like me alone."

Reichental has had little time to dwell on the meeting that never was but remained perplexed as to why she had sought him out.

"I was certainly not disappointed she didn’t agree to meet me, but I was certainly distressed to learn of her continued denials," he said. "It is just as well we didn’t meet, perhaps, because shaking her hand would be something I would have regretted for the rest of my life."

© 2015 The New York Times Company