Nick Cassavetes' ex-wife has fired back at him after he accused her of stealing their child ... she says the famed director has engaged in shocking conduct that has forced her and her daughter underground.
Heather Wahlquist tells TMZ Nick is actually the one who stole the 13-year-old back in August, and claims it was done out of revenge.
Heather claims Nick sent a pic to their daughter showcasing his exposed ass. She also mentioned that he posted a meme of Kevin Spacey along with several games with the caption, "Who remembers having to blow these as a kid." The words are followed by emojis of women raising their hands.
She insinuates Nick is still upset she left him 5 years ago, saying he's now in a "revenge plot against my family and I'm terrified."
Heather says she spent Xmas Eve alone with 13-year-old Barbie, "scared that this will end bad." She claims Nick has parked outside her home, "taking pictures of us and following us all around town."
And there's this ... Heather acknowledges Barbie "loves her papa" and says she's heartbroken.
We reached out to Nick ... so far no word back.