Her 19-year-old mother gave sparse details -- her name, that Stacy's father was an American soldier, that her family came from the Can Tho region in Vietnam's Mekong Delta. But not why she gave up Stacy. "So, there's a part of it that still hurts," she told Petersen. "And I miss her. I miss her terribly."
"Explain that to me: How do you miss someone that you certainly couldn't even remember?"
"I miss the idea of having her in my life," said Stacy. "The fact that she kept me for a couple years before she gave me up, to me, tells me that she loved me very much, and she tried. She did what she could."
It's a long trip back to Vietnam -- not just the hours on a plane, but the trip back in time.
In Saigon (now Ho Chi Minh City), Sister Mary Nelle takes Tobi to her orphanage. It is still operating, still a place for abandoned babies.
"How do you feel when you see these babies and this is where you came from?" Petersen asked Tobi.
"Just very amazed and humbled," she replied. "And I can't believe that this could be the very room that I was nourished in."
Perhaps only a child who never knew her birth parents or even her homeland can understand how important this moment is -- finding at least this much of her beginnings.
"I can't put words to it. Can't believe that," said Tobi.
"This is where you came from," Petersen said.
"It is. My life started here because of people who cared so much. And they had hope for us."
But for Stacy, the journey might be more revealing -- and come with more answers.
In Ho Chi Minh City, she connects with a Vietnamese TV network, together with a man who's been tracking down the families of orphans -- and discovers they may have located hers.
"I'm scared that it's not them," said Stacy. "I'm scared of getting my heart broken."
To meet them, she and her husband, Peter, travel to Can Tho, 100 miles to the south. The possible relatives stand ready to welcome this American woman into their home.
But what might be the best of news, is also the worst. If this is the right family, then Ngo Thi Diep (who may be her mother) died of cancer.
Stacy has a great likeness to her mother, says Uncle Hai.
Her aunt said her mother always missed her, that she tried all her life to find her.