Kate McCann has told of her fears that the "lovely" sight of her daughter Madeleine in a new outfit may have led to her kidnap.
The doctor said certain images of Madeleine were forever etched in her mind, including a memory of the three-year-old in a peach smock top and shorts.
Mrs McCann bought the outfit especially for a family holiday in Portugal, where Madeleine was snatched from their apartment four years ago, shortly before her fourth birthday.
In an extract from her book, Mrs McCann said of the new clothes: "A small extravagance, perhaps, but I'd pictured how lovely she would look in them and I was right." She added: "I was following her with my eyes admiring her. I wonder now, the nausea rising in my throat, if someone else was doing the same."
Mrs McCann's last photo of Madeleine shows her wearing the new top and sitting with father Gerry and younger sister Amelie by the pool on the day she vanished. "Heartbreaking as it is for me to look at it now, it encapsulates the essence of Madeleine - so beautiful and so happy," the 43-year-old said.
Mrs McCann had been dining with her husband and seven friends at a tapas restaurant 100 metres from the youngster's room in the resort of Praia du Luz when Madeleine vanished.
In another extract from the book, which is serialised in the Sun, Mrs McCann told how the couple had considered the Ocean Club resort to be a "safe, family-oriented" place. "Later we were told by British police that the ground floor location, access to roads front and side, secluded entrance and partial tree cover made our apartment a prime target for burglars and other criminals. Never once did this occur to us when we arrived."
She said they would always regret the decision to leave their three children in their room while they dined, checking up on them regularly. But she added: "It is easy to be wise after the event. I can say, hand on heart, it never occurred to me that it might not be a safe option."
In an interview with the Sun, Mrs McCann told how she will never give up hope on finding Madeleine, and is convinced she is still alive. She said: "Certainly in my heart I feel she is out there. We'll never give up on finding her, how could we? What parent would give up on their child?"
Mrs McCann's book, called Madeleine, is published on Thursday, the day of Madeleine's eighth birthday. Proceeds from the 384-page book, which Mrs McCann has written herself without the aid of a ghost writer, will boost the dwindling fund to search for her daughter.