May 1, 2008 -- A year has passed since 3-year-old Madeleine McCann vanished without a trace during her family's vacation in Portugal. Her parents, Kate and Gerry McCann, have waged a public battle to find Madeleine and endured their own private hell after being named as suspects in her disappearance by Portuguese police.
The McCanns say they are haunted by the possibility that Madeleine's cries the night before her disappearance may have been a hint that she had seen a stranger lurking around the hotel room or something that made her uncomfortable.
Watch "20/20" this Friday at 10 p.m. ET for more of the exclusive interview with Kate and Gerry McCann.
In mid-April this year, as the McCanns campaigned for a European Amber Alert system, sealed statements the couple made to Portuguese police about Madeleine's cries the night before became public.
According to the leaked statements, on the morning of their last day together, Madeleine asked her mother, "Mummy, why didn't you come when we were crying last night?"
"It was sort of fairly early in the morning, she just very casually really said, 'Where were you last night when me and Sean cried?' and we immediately looked and said, 'When was this Madeleine, was this when you were going to sleep?'" said Kate McCann.
"We obviously told the police because we thought, does this indicate that someone has been round the night before and that's what has woken her up?" she said. "Which is significant you know … I've persecuted myself over and over again about that statement because you think, why didn't they [the police] kind of just hold it and say, 'What do you mean?'"
Madeleine didn't answer her parents' question and "carried on playing, whatever she was doing, totally undistressed," Kate McCann said.
The McCanns say that because Madeleine didn't make a big deal about the issue that they let the matter go. But they say they consciously decided that evening to be more vigilant about checking in on the children.
The couple has faced harsh criticism for leaving their children alone in the resort condo while at dinner the night Madeleine disappeared.
The McCanns say the leak was no accident and was meant to make them look negligent. The couple believes police in Portugal are responsible for the leak, a charge which the police have strongly denied.
The McCanns try to reassure themselves that Madeleine would have told them if she saw someone or something strange.
"As Gerry said, 'She's a very bright little girl, and if Madeleine had something to say she'd say it,'" Kate said. "And also bearing in mind that that night, the night that she went, she said that had been the best day of her holiday, so she certainly wasn't upset by anything."
For more information on Madeleine McCann: http://www.findmadeleine.com/