The father who adopted a young ‘child’ has shared the telltale signs that she was actually an adult, saying he was left wondering: “Who the f**k is this person?”

Kristine and Michael Barnett adopted Natalia Grace back in 2010, believing her to be a six-year-old girl with a rare bone growth disorder.

However, as time went on, it transpired that she wasn’t who said she was - with the Barnetts saying she was secretly an adult attempting to harm their family.

Investigation Discovery

The stranger-than-fiction story has become the subject of a brand new documentary, The Curious Case of Natalia Grace, which explores the Barnetts’ accusations of their adoptive daughter being a fraudulent 'adult sociopath masquerading as a child'.

In the first episode, Michael discusses the signs that he and Kristine noticed in the first few months after adoption - including one incident immediately after they picked up their ‘brand new’ daughter.

He recalls: “We get to the hotel that night, and Kristine’s going to give our brand new daughter a bath, and I hear a shout from the bathroom.

“This was a, ‘I’m not playing around, come here right now, Michael’ shout.

“I get up and go flying to the bathroom, and the colour’s almost gone from her face. It’s almost like she’s seen a ghost. She’s truly frightened and she just doesn’t know what she’s seeing or what’s going on.

“She says, 'Michael, look. Look down'.

Investigation Discovery

“And Natalia had full pubic hair. And I don’t know what you think. Is that possible? Is that even possible? Who the f**k is this person?”

Michael said he and his wife vowed to show ‘love and compassion’ to Natalia after the bizarre discovery, as these were things she hadn’t experienced before.

However, things took another turn when she admitted to having already started her period.

He continues: “There was a day where I came home from work, Kristine’s got a pair of Natalia’s underwear.

“Kristine asked Natalia to tell me what’s going on.”

A home video then shows Kristine asking Natalia to explain to her dad ‘what happened’.

Investigation Discovery

Michael continues: “I can remember her physical-ness at the time, her hands were just out in front of her like this, and she’s like, 'Well, I have a period, and I’ve been hiding it'.

“And I just don’t know what’s going on right now.”

Michael can then be heard in the video telling his wife it’s simply ‘not possible’.

A family friend also says that Kristine had found some socks that she had used in her underwear and thrown them out of the window.

“Kris was just mortified,” they say.

“She said, ‘This isn’t normal. What have I got myself into?’

“And I said, ‘You need to start finding out how old she is’.”

Later in the documentary, we also hear how Natalia was sent to a state mental hospital, where she had to be transferred to the adult wing after staff discovered her pubic hair.

Various employees are interviewed anonymously via phone in the six-part series, with many saying Natalia could be ‘manipulative’ and ‘aggressive’ towards others, ‘talked about sex a lot’ and even started ‘propositioning the men’.

The Curious Case of Natalia Grace will air for three consecutive nights on Investigation Discovery starting on 29 May.