Madeleine McCann's parents have admitted to being left "haunted" at a question their 3-year-old daughter asked the morning of her disappearance.
Maddie disappeared from the family's apartment on the evening of May 3, 2007, while on holiday in Portugal.
But in Kate McCann's book, Madeleine McCann: Our Daughter's Disappearance and the Continuing Search for Her, the 51-year-old mother detailed their concern for Maddie just hours before she disappeared.
In her book, which was released in 2011, Kate says a question Maddie asked her left her "puzzled" and now "haunted".
"At breakfast time, Madeleine had a question for us: 'Why didn't you come when Sean and I cried last night?'," she wrote.
Kate wrestled in her head what Maddie had meant and wondered if her daughter had meant they cried while they were out for dinner.
That particular theory worried Kate, according to the account in her book.
"Gerry and I were disconcerted, could Madeleine and Sean have woken up while we were at dinner?
"If so, it was worrying, obviously, but it did not seem probable.
"As I've said, not only did they rarely stir at all at night, but if they did it was hardly ever, and I mean ever, before the early hours.
"If they had done so on this occasion, it would mean they had woken up, cried for a while, calmed themselves down and fallen asleep again."
"But it is my belief there was somebody either in or trying to get into the children's bedroom that night, and that is what disturbed them," Kate McCann said. Photo / Getty
Kate says the idea both her children waking up and not being noticed by their parents during the night is unlikely.
"All of this would have been in the space of 30 or 45 minutes.
"Children usually need some soothing back to sleep once they've woken, especially if two of them are awake and upset at the same time.
"It seems highly unlikely they would have gone through all these stages without one of them overlapping with one of our checks.
"It was not impossible, but it seemed implausible.
"Not for a moment did we think there might be some sinister reason for this occurrence, if indeed anything had occurred.
"If only foresight came as early to us as hindsight.
"Within hours, the explanation for this would seem hugely important, and so haunted have I been ever since by Madeleine's words that morning that I've continued to blame myself for not sitting down and making completely certain there was no more information I could draw out of her.
"This could have been my one chance to prevent what was about to happen, and I blew it.
"There was absolutely nothing to give me any reason for suspicion and we can all be clever after the event.
"But it is my belief there was somebody either in or trying to get into the children's bedroom that night, and that is what disturbed them."
A view of the Ocean Club apartments in Praia da Luz. Photo / Getty
In her book, Kate also explains the system of "child-checking" that the McCanns and their group of friends had decided on, as they dined in the resort's tapas restaurant close by.
She says: "We now bitterly regret it and will do so until the end of our days."
The recent spotlight on Maddie's disappearance comes following the Netflix series The Disappearance of Madeleine McCann.
The eight-part documentary was not supported by the McCann family.
