Mariclare Costello, who played teacher Rosemary Hunter on The Waltons as well as Emily in the cult classic horror film Let's Scare Jessica to Death, has passed away.

In 1964, Costello was one of only 30 to be selected for the Lincoln Center Repertory Company out of hundreds of hopefuls. By 1967, she made her onscreen debut with the black comedy movie The Tiger Makes Out, which was also Dustin Hoffman's first film.

In 1971, Costello starred in the cult classic horror movie Let's Scare Jessica to Death. The image of her rising from the lake in a wedding dress may be the most iconic scene from the film. Though the movie received mixed reviews at release, it has since been reassessed as a classic and ranked among lists of the best horror films of all time.

Shortly afterwards, Costello joined the cast of The Waltons as schoolteacher Rosemary Hunter. Her character was the first to read one of John-Boy's stories and encourage him to send it off to one of the big magazines in New York. In the season four premiere, she was married to the Reverend Matthew Fordwick, played by John Ritter. The writers included Costello's pregnancy in the show in season five.

Costello left The Waltons to star in the CBS series The Fitzpatricks, a drama about a family living in Flint, Michigan, but the series only ran for thirteen episodes.

Costello continued to appear in guest roles on TV shows like Hart to Hart, Murder, She Wrote, In the Heat of the Night, Judging Amy, and more. She largely stopped acting onscreen after the 90s, pivoting to directing stage productions and teaching acting at a university. She led a theater group at Homeboy Industries, a gang rehabilitation and re-entry program.

In her personal life, Costello was married to Allan Arbus, known for his role as psychiatrist Dr. Sidney Freedman on M*A*S*H.

The actor and professor was 90 years old.