It was April 15, 1945, in the notorious Bergen-Belsen concentration camp, when the two were just teenagers.
The Nazi death camp was liberated that day, but Harold says he felt weary, and near death.
"I, at that point, fell to lie down and meet my maker," he said, speaking to students at Crestwood Preparatory College in Toronto on Tuesday.
And he likely would have died in the concentration camp, where many were suffering from typhus, starvation and dysentery, had it not been for Nancy.
She walked into the room where Howard lay and spotted him on the floor among the corpses.
Nancy had seen Howard a few times before, when she used to visit her older brother in his barracks.
"He had his eyes open, moved a little, looked kind of very sick," she said.
Took care of Howard for 3 weeks
Nancy's companions were skeptical that he could be saved, but she persisted.
"I said, 'You're right, he's very sick, but if we let him lie here, he'll never get better and he'll die.'"
Nancy took Howard to a room left vacant after the Germans fled and laid his limp body down on one of the bunk beds, a luxury after sleeping on the hard floor for so many years.
For almost three weeks, she tried to nurse him back to health. Nancy says she wanted to do "a good deed," because she felt guilty that she was the only one from her family — five brothers — to survive.
Howard was lifeless, and Nancy didn't think he was going to make it.
"He couldn't move from his bunk bed," she said. "He couldn't do anything, really."
Then one day, Howard disappeared, Nancy said.
"We went out to get some food, we come back and he was gone," she said. "So, we didn't know what happened."
Unbeknownst to her, British soldiers found Howard and took him to a military hospital.
Reunited in Toronto
It took him six months to recover, and Howard emigrated to Toronto soon after. A month later, he found out that the girl who saved his life was in the city, too.
Howard managed to find Nancy and showed up at her door, with flowers.
"I said, 'You remember me?' She says, 'Oh, it's you?' And I started to say thank you for saving me," Howard recollects. "How many times can you say 'Thank you for saving me?' I was lacking words in what to say."
Three years later, the pair got married. That was 63 years ago, and now, they have four children, nearly a dozen grandchildren, two great grandchildren, and still look at each other lovingly. They're both retired, and live in Downsview, Ont.
The Kleinbergs cite a Jewish word to describe how they met.
"'Beshert' means 'it's meant,'" Howard told CBC News. "God's will".
Their advice to young couples is to respect each other.
"You kiss her good morning and you kiss her goodbye. It helps," he said. "And always open the door for her."