Selma Blair lost out on a lot of opportunities after her late father's girlfriend sent out anonymous letters claiming Blair was a drug addict.

The actress shared in her memoir, “Mean Baby: A Memoir of Growing Up,” that she first went into rehab at age 22. There, she was given a drug called Trexan — to curb a desire to drink — but it caused terrible side effects and left her feeling “rageful” and “agitated.” One day during a panic attack, she accosted a nurse, according to Page Six.

“The doctors discontinued the Trexan. Poof, I was normal. My rage vanished. What I didn’t know at the time was that my father had witnessed this entire episode. He had come to visit me and stood silently in the hallway watching the scene unfold. Later, he would use that episode against me,” she wrote.

Once she got out of rehab, she began work on the 1998 film “Arresting Gena.” But her problems were far from over.

“That’s when the letters started coming. Twenty letters a day arrived via FedEx at the production office of ‘Arresting Gena,’ all of them written by a mysterious sender. They contained bogus information about me and my ‘violence and addiction,'” she wrote.

The letters continued coming in for the next 18 months, during which she was fired from every job offer she had in hand.

Soon, Blair was contacted by a detective retained by the talent agency UTA. He told Blair that he’d been hired to protect Drew Barrymore because she was allegedly writing death threats to Barrymore. After weeks spent trailing Blair, the detective realized she wasn’t the culprit. He also told her that he had some information about the letters’ origin.

“He said the letters were being mailed from my father’s office building in Detroit. He gave me a description of the sender that just happened to match my father’s girlfriend at the time, I found out,” she wrote.

The detective then told Blair to set a trap to find the poison pen author. At the time, the "Cruel Intentions" star had secured a screen test for a movie called “Father’s Day,” and taking the detective's words into consideration, she told three different stories to three different people.

“I told my ex-boyfriend that I had a screen test against Alyssa Milano. I told a friend I had a screen test against Alicia Silverstone. I told my father I had a screen test against Drew Barrymore," she penned.

“The head of casting at Universal received no fewer than fifteen letters saying I was a violent and dangerous person who held a grudge against Drew Barrymore. The casting director showed me and my agent, Jana, the letters,” added Blair.

Selma Blair
Actress Selma Blair at the Hammer Museum Gala in the Garden honoring Laurie Anderson and Todd Haynes sponsored by Bottega Veneta, in Westwood, California, Oct. 8, 2016 Getty Images

Once she realized who was behind the letters, she called her dad, Elliot Beitner. The “Legally Blonde” star was devastated and told her father that “he was now dead to me. I didn’t speak to him for twelve years, and our relationship, already challenging, never fully recovered.”

Beitner died in 2012.

Years later, Blair also met Barrymore in a bid to make amends. “I discovered she’d never truly known the whole story, only that it was a father thing, a messed-up situation. I told her I was so, so sorry about the letters she’d received. She hugged me and said, ‘Don’t worry. We all have wild family stuff,’ and her big embrace smoothed out some of those years-old anxieties,” explained Blair.