A supposed 'adopted child' who was later revealed to be a 22-year-old woman began displaying troubling signs that indicated she was not a child.

Back in 2010, Michael and Kristine Barnett, a couple from Indiana, thought they had adopted a six-year-old orphan named Natalia Grace from Ukraine. They had intended to expand their family through this adoption.

However, they were taken aback when they started observing certain 'peculiar' behaviors in Natalia.

Check out the trailer for The Curious Case of Natalia Grace below…

The couple noticed several physical signs in the child they believed to be six years old, including the presence of pubic hair, adult teeth, and a monthly menstrual cycle.

Upon conducting medical tests, it was revealed that the individual was actually a 22-year-old woman who had a form of dwarfism known as spondyloepiphyseal.

According to the Children's Hospital of Philadelphia, spondyloepiphyseal is a rare genetic disorder that affects bone development, particularly in the spine and long bones of the arms and legs, leading to short stature and skeletal anomalies.

The remarkable story has been transformed into a docuseries titled The Curious Case of Natalia Grace, providing viewers with an authentic account of how this perplexing situation unfolded.

In the series, the family shares the initial signs that raised suspicions about the girl they had believed to be their child, highlighting the bewildering nature of the events.

Michael said: "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."

The father hurried to the bathroom, finding his wife in a state of shock and fear. She urgently told him to "look down," and when he did, he saw that their child had developed full pubic hair.

"I don't know what you think. Is that possible? Is that even possible? Who the f*** is this person?" he asked.

Despite their surprise, Michael made a promise to demonstrate "love and compassion" towards their adopted daughter.

However, the situation began to deteriorate rapidly.

"There was a day when I came home from work, Kristine's got a pair of Natalia's underwear," Michael continued.

"Kristine asked Natalia to tell me what was going on. 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."

The family became increasingly perplexed as the events unfolded, as Natalia's actions were not expected given her presumed age. The situation took a serious turn when she made attempts to harm the other children in the household.

Kristine later revealed that she had witnessed Natalia drawing pictures with a disturbing content, expressing her desire to harm family members. Additionally, Kristine observed Natalia tampering with her coffee by adding "chemicals."

The parents also shared alarming incidents such as finding thumbtacks deliberately placed on the staircase and Natalia attempting to pull Kristine towards an electric fence.

As the situation escalated, Natalia was eventually admitted to a children's psychiatric hospital. However, staff soon transferred her to an adult ward after discovering her physical development, including the presence of pubic hair.

Attorney Beth Karas spoke to TMZ about the documentary, shedding light on the backstory and providing additional insights.

"[The family] went to the court with an emergency petition and an affidavit from a doctor who had been treating her for the past few years who said that he did not notice any growth and there was no growth in four years," she shared with the publisher.

"She was supposedly eight at the time. So he said, 'Well, you stop growing when you're 18. If she hasn't had any bone growth in four years, then she's at least 22'."

"And with a stroke of a pen, he went from age eight to 22 for Natalia. So she theoretically became somebody who could vote, drink, and drive."