It has been 1,717 days since Israeli soldier Gilad Shalit was captured by Hamas, and Karnit Goldwasser is counting. Ms. Goldwasser—the stalwart widow whose two-year fight for the release of her kidnapped husband, Ehud, ended only when his body was returned in a 2008 Israeli-Hezbollah prisoner swap—is counting because she cannot stop, will not stop.

Her petite frame and freckled face lend an appearance younger than her 34 years, but her voice ages her as she describes the ongoing task of ensuring that Gilad Shalit, like her late husband, is not forgotten. “‘All for one and one for all’ is not just a statement in Israel, it’s a way of life,” Ms. Goldwasser said at a café in midtown Toronto, where she will spend the next two days encouraging Canadians to take up Mr. Shalit’s cause. “For me, this is the same as if someone was injured during combat and he is lying there in the middle of a firefight. Someone must go out there and help him.”

Mr. Shalit, who was 19 when he was captured at the Kerem Shalom border crossing and whose whereabouts in the Gaza Strip are still unknown, was kidnapped three weeks before Ms. Goldwasser’s husband and another Israeli soldier, Eldad Regev, fell into the hands of Hezbollah—the Lebanon-based Muslim group supported by Iran and Syria.

Later that summer, once the 2006 Lebanon-Israel conflict mostly subsided, the three families met at the law offices of Ya’akov Ne’eman, the current Israeli Minister of Justice, to pool their energies and foster a plan.… “The point of the meeting was not to hug each other and say everything would be alright—you don’t have time to be emotional,” Ms. Goldwasser said.… “The point of the meeting was to work together, to think together.…”

Ms. Goldwasser’s tenacity led to meetings with now-U.S. Secretary of State Hillary Clinton, former U.S. president Bill Clinton, French President Nicolas Sarkozy, and the Pope, all in the hopes that maybe—just maybe—she could convince them to lean on the Red Cross to demand a visit with her husband.

In 2007, she snuck into a press conference in New York and faced off with Iranian President Mahmoud Ahmadinejad, insisting to know why he would not allow the Red Cross to see…her husband.… The incident garnered international attention and, although the Red Cross never did visit [Ehud], she hopes the outcome will be different for Mr. Shalit and his family. “If someone could go and visit Gilad Shalit, and then go back to his mother, Aviva, and say, ‘I saw your son, he looks good. He’s quite sad, but he’s okay. He’s asking you not to worry’—try to imagine what that would mean for his mother,” said Ms. Goldwasser.… “Imagine what it would mean for Gilad Shalit, who is sitting alone over there and no one has yet visited him. Imagine if someone went to him and said, ‘From here, I am going to see your mother and I’m going to tell her that you’re OK’.”

Ms. Goldwasser said she is not under the illusion that a rally or a media interview will secure the release of Mr. Shalit, but she said that if enough people become “ambassadors for Gilad”—that is, if enough people speak “loudly and clearly,” and “keep Gilad on the agenda”—then maybe the pressure will culminate in a visit from a non-governmental organization. “It has been 1,716 days that he has been in captivity, and I worry that he thinks we have forgotten him,” she said. “Who knows if he’s aware that we’re fighting for him.”

It has been more than two years since her husband’s coffin was returned to her, and Ms. Goldwasser has certainly not forgotten.… “This issue has changed me, I have become different—it has changed my personality, maybe I am more mature,” said Ms. Goldwasser.… “I paid a very, very high price for my country, so it’s more hurtful to me now when something bad happens in Israel.”

Since [her husband’s body was returned in the] July 16, 2008 prisoner swap, [Ms. Goldwasser has visited the Shalit family at their protest tent next to the Prime Minister’s house in Jerusalem on several occasions. “They are sitting, and they are waiting.… They are there to remind the government of their son.…”

But the return of Mr. Shalit is about far more than the return of one man, Ms. Goldwasser said: Young men and women join the Israeli army every single day, and they must be confident that the Israeli government is their greatest protector—that its politicians will do whatever it takes to secure their return. “No matter how [we get] Gilad, we’re going to bring back our values and our self-confidence,” she said.… “It’s about the message and our confidence in our country.”