New Docuseries Unravels Bizarre Mystery Of Adopted Ukrainian Natalia Grace

A mysterious adoption more than a decade ago is getting the spotlight thanks to an upcoming docuseries … about a Ukrainian girl who allegedly tried blending in as a small child and attempted to murder her new family.

Attorney Beth Karas joined us on “TMZ Live,” giving us the scoop ahead of the first episode of ID’s “The Curious Case of Natalia Grace” … which follows an American fam that adopted Natalia back in 2010, only to discover she was MUCH older. A few years in the parents believed she wasn’t 8 years old … they were sure she was around 22.

Beth says Natalia repeatedly threatened her new family with knives and even tried poisoning them.

Natalia’s child persona had folks split on whether she was a kiddo or fully grown — she would interact with young children as if she were a peer but also displayed an adult side.

Her tale has often been compared to the horror flick “Orphan” … which came out the year before Natalia’s adoption and is based on a horrifyingly-similar story.