Nathaniel died on April 15, 2011, just two weeks before his sister Carrie's graduation from college. She had signed up for a walk along Spain's ancient pilgrimage route, Camino de Santiago, but in her grief, Carrie told her parents she couldn't do it alone.
So, they offered to walk the second leg with her. That was when Denis Asselin got the "Camino fever" and an urge to keep walking to ease the pain.
"It is powerful -- just the feet hitting the ground," he said. "It's a conduit for some of the pain and sorrow deep inside. And you are moving, not sedentary. It's like a cleansing that's happening -- and you are doing something."
After the trip, Denis Asselin thought about crossing the Pyrenees, but later it "seemed a little contrived -- a little artificial."
"The ancient Pilgrims walked out the front door where their journey began," he said. "And then the trajectory came to me."
Asselin got the unwavering support of his family and the OCD Foundation. After four preliminary walks to places where Nathaniel had found joy in his short life, he headed north. Next week, he will cross the final finish line at a rally at Christopher Columbus Park on the waterfront in Boston.
The journey has been hard on his feet, but good for his heart.
"My motivation is that if every day five people learn what BDD is about, it will be well worth it," said Asselin.
As for Judy Asselin, she has derived courage and strength from his walk and intends to join him next week with their daughter.
All, are healing in their own way.
"Nathaniel was the center of our orbit for so long that having him gone throws us all out of whack; but then, so did his disorder," she said.
"He was a gem of a human being, but watching him suffer became less and less tolerable," Judy Asselin said of her son. "My challenge will be learning to accept the injustice of his suffering and death. It just isn't fair ...
"Finding the cause and better treatment seems to be the only path to that goal."