While Serling wrote a number of wonderful scripts for that show (including "A Stop at Willoughby," "Walking Distance," "The Shelter," and "On Thursday We Leave for Home"), he was one of three writers whose work made TZ the marvel that it was.
The other two were Charles Beaumont and Richard Matheson. Beaumont died in 1967, struck down by something like a mutant form of Alzheimer's; at the time of his death at the age of 38, he looked like he was in his 90s. The disease had affected his ability to work; Beaumont contributed a lot of excellent scripts to TZ, but the heavy lifting on a few of the last Beaumonts was done by his friend Jerry Sohl.
Richard Matheson, last of the three, died last month at the age of 87, closing one of the great careers in American popular fiction. His novels included The Shrinking Man, I Am Legend, Hell House, and Bid Time Return (better known as Somewhere in Time). His work as a novelist was not limited to the horror and fantasy genres. He wrote westerns (A Journal of the Gun Years, A Gun Fight), suspense novels (Hunted Past Reason, Ride the Nightmare), and a novel of World War II called The Beardless Warriors.
If he had written only The Shrinking Man, I Am Legend, and Bid Time Return, I think he'd have a permanent place in the memories of genre aficionados. But Matheson was a master of the short story as well as a novelist. Nobody who's read them forgets classic chillers like "Prey," "Born of Man and Woman," "Duel," "The Children of Noah," "Nightmare at 20,000 Feet," or "Button, Button," to name only a few. His short fiction is usually kept in print along with his novels and excellent collections are available at this writing both in print and ebook formats.
Matheson was also a superb screenwriter, often adapting his own work for film and television. He was the screenwriter for the best of the Roger Corman adaptations of Poe in the early 60s, and with Charles Beaumont he adapted Fritz Leiber's Conjure Wife for the excellent horror film Burn, Witch, Burn. Adaptations by Matheson from his own novels included The Incredible Shrinking Man, Somewhere in Time, The Legend of Hell House, and The Last Man on Earth (the only film version of I Am Legend that bears any resemblance to the original novel).
He adapted a number of his own short stories for television. Best known, perhaps, are "Duel" for the Spielberg film, and "Prey" for the climactic segment of Trilogy of Terror. But Matheson's work for television is most easily found in the original Twilight Zone, and his episodes provided many of that series' finest moments. The two episodes starring William Shatner, "Nightmare at 20,000 Feet" and the lesser-known "Nick of Time," were Matheson scripts. So were "Steel," "Mute," "Little Girl Lost," "Late Night Call," the uncharacteristically light-hearted "A World of His Own," and others. "Nick of Time," with its depiction of a man on the verge of letting his superstitious fascination with a diner's fortune-telling machine imprison him forever in a small Ohio town, is a perfect example of Matheson's ability to show nightmares lurking behind the surface of everyday surroundings.
"Death Ship," for TZ's fourth season, is to my mind a real stand-out in Matheson's work for the series. The original story, dealing with a spaceship crew who land on an alien world and find what appears to be their own crashed vessel and their own bodies dead inside it, is a nice science-fiction-horror story, well worth a read (and you can find it in his collection Duel and Other Stories). But Matheson's translation of this story into a one-hour TZ episode is nothing short of marvelous. Scenes in the script that were not in the original story expand and enrich the characters rather than simply padding the narrative for length, and the final confrontation between Lt. Mason and Capt. Ross has an intensity not found in the concluding paragraphs of the short story -- that the scene is performed by a pair of powerhouse actors like Ross Martin and Jack Klugman helps, but the strength of the material is all there in the writing. The episode is a wonderful example of TZ at its best, it remains as gripping on repeat viewings as it was on the first, and it's one of the very few instances of a film adaptation equal to the original source material.
So raise a glass to Richard Matheson, one of the best, and check out his books (http://www.amazon.com/Richard-Matheson/e/B000AQ285E), and some of his work for film and television (http://www.imdb.com/name/nm0558577). You won't be disappointed. And if you've read or seen these before, take a little time to revisit them -- chances are you'll enjoy them as much as you did the first time, and maybe even more.