Michael McEachern McDowell, 49, the author of a score of horror novels who went on to script such classic offbeat motion pictures as director Tim Burton's "Beetlejuice" and "The Nightmare Before Christmas," died Dec. 27 at a hospital in Boston. He had AIDS.

He also wrote for the TV series and movie "Tales From the Darkside." Since being diagnosed in 1994, he had taught screenwriting at Boston University and Tufts University and continued to write commissioned screenplay treatments. At the time of his death, he was working on treatments of a "Beetlejuice" sequel and a new version of "The Nutcracker."

Dr. McDowell was born in Enterprise, Ala. He was a summa cum laude English graduate of Harvard University and received a doctorate in English from Brandeis University.

Although he began writing in college, he supported himself by working as a teacher, a theater critic and a Massachusetts Institute of Technology secretary before royalties started paying his way.

His first two novels, both with supernatural themes, were "The Amulet" and "Cold Moon Over Babylon." Then, in 1983, he wrote six serial paperback novels, one published each month by Avon, known collectively as the Blackwater novels. Titled "The Flood," "The Levee," "The House," "The War," "The Fortune" and "Rain," they chronicled the history of a Southern family over more than 60 years.

"McDowell's strengths are many," author and critic Alan Ryan wrote of the Blackwater serial in The Washington Post. "His prose is rich, allusive, and often intricate, yet so smoothly polished that it never distracts from the table."

Dr. McDowell teamed with Dennis Schuetz under the joint pseudonym Nathan Aldyne to write four gay detective novels: "Vermillion," "Cobalt," "Slate" and "Canary."

Dr. McDowell later moved into TV writing, penning scripts for such series as "Tales From the Darkside," "Steven Spielberg's Amazing Stories" and a syndicated stepchild of "Tales" called "Monsters." He also wrote for the TV series "Alfred Hitchcock Presents" and TV specials "Lover Come Back to Me" and "JFK Conspiracy."

Joining Burton, he wrote the screenplay for the 1988 "Beetlejuice" along with Warren Skaaren, based on an original story by Dr. McDowell and Larry Wilson about a dead couple returning home. The film became a cult favorite and spun off a long-running stage show at the Universal Studios Hollywood amusement park.

Dr. McDowell went on to write screenplays for the ghostly 1988 farce "High Spirits," starring Peter O'Toole and a little-known Liam Neeson; "Tales From the Darkside: The Movie," starring Christian Slater in 1990; the whimsical, animated "Nightmare Before Christmas" in 1993; and "Thinner," which was based on horrormeister Stephen King's story and released in 1996.

Survivors include his companion of 30 years, Laurence Senelick of Medford, Mass.; a brother; and a sister.