Before the sappy “Twilight” movies there was another “Twilight” that shone far brighter and lasted far longer. It was, of course, Rod Serling’s “The Twilight Zone,” which makes its 20th yearly orbit on the Syfy Channel’s marathon on Dec. 31.

“There is a fifth dimension beyond that which is known to man…” Serling would begin the anthology, his mouth taut, his voice staccato and mesmerizing.

Each episode was a small morality play played out in modern times. They were stories that could be taken on several levels - from the simple roundelay of a tale to a shattering subtext with deeper meaning ñ all in the context of science fiction.

“The Twilight Zone,” which beamed up long before “Star Trek,” “The Outer Limits,” or “The X-Files,” became one of the most popular series ever on TV and marked Serling as one of the first creators to bring timeless writing to the television medium.

Serling, who died 39 years ago of complications following heart surgery, earned Emmys for “The Twilight Zone,” as well as dramatic TV plays like “Patterns,” “Requiem for a Heavyweight,” “The Comedians” - which were part of TV’s live, Golden Age.

A veteran of World War II’s Pacific campaign, Serling was a wiry, tough guy who’d once been a Golden Gloves boxer.

But he was a very shy man, said the late Ernest “Buck” Houghton, who produced the first 100 episodes of “The Twilight Zone.”

“He was a very complex man, a very nice man, a very cooperative man who had a social conscience that he tried to put into his stories, and who was even-tempered in a high-temper business,” said Houghton. “He never believed that he was nearly as talented as he was.”

Serling began writing for radio shortly after the war. He moved into television scripting for many of the top shows of the day including “Studio One,” “The U.S. Steel Hour,” “Playhouse 90.”

There were 156 episodes of “The Twilight Zone,” with Serling writing 92 of them. Eighty of those aired the first three years of the series, which began with a 30-minute anthology. At the beginning of the fourth year it was expanded to one hour, but the longer format was discontinued the following year.

“The Twilight Zone” marathon runs Dec. 31 from 8 a.m. to 5 a.m., concluding Jan. 1 from 6 a.m. to the following 6 a.m.