A tourist who was staying in the flat above where Madeleine McCann was staying with her family claims to have seen a 'prowler' opening the gate just hours before the little girl disappeared.
Carole Tranmer was staying at the resort in Praia da Luz at the same time as the McCanns back in May 2007.
The new eight-part documentary series puts forward a number of theories. Credit: Netflix
Speaking on the new Netflix documentary The Disappearance of Madeleine McCann, investigator and author Anthony Summers shares information about the sighting saying: "Carole was looking out of the window.
"She said, 'Looking down below the McCann flat I saw someone come out of the ground floor apartment closing the gate very carefully and quietly.
"'It looked very strange to me.
"'He looked to one side and the other, shut the gate and walked very quickly below.'
"This is on the afternoon of the day Madeleine is going to disappear.
"What had struck her as peculiar, she said, was 'the way the man had closed the little gate down there'."
The eight-part documentary takes a detailed look at the case and events leading up to the disappearance of the Maddie.
Madeleine was on holiday with her parents Kate and Gerry and her twin siblings Sean and Amelie, when she vanished without a trace on 3 May 2007.
On the night of her disappearance, her parents were out at a tapas bar with some friends near to the apartment where they were staying.
Madeleine and her brother and sister were left to sleep in the apartment, with Kate and Gerry taking turns to go and check on their kids at regular intervals, the documentary states.
However, at 10pm when Kate went to check she found that little Maddie's bed was empty.
The documentary explores a number of theories on what could have happened to the little girl.
One theory is that a man got into the apartment and snatched the little girl while she slept.
In a creepy scene that left viewers freaking out, a re-enactment of what might have happened featured a man entering the toddler's room wearing a surgical mask - suggesting she was drugged and then taken from her bed.
Both Kate and Gerry refused to take part in the documentary, saying they felt it would just serve to fuel conspiracy theories and could hinder the on-going search for the little girl.
The Disappearance of Madeleine McCann is now available to stream on Netflix.
Featured Image Credit: PA