It was Noel Coward’s partner, Gertrude Lawrence, who encouraged Tom to try acting. He made his Broadway debut in 1952 in the chorus of the musical Wish You Were Here. He also worked in television at the time, but as a production assistant. In 1955, he moved to California to try his hand at the movies, and the next year made his film debut in The Scarlet Hour (1956). Tom was cast in the title role of the Disney TV series Texas John Slaughter (1958) that made him something of a household name. He appeared in several horror and science fiction films: I Married a Monster from Outer Space (1958) and Moon Pilot (1962) and in westerns: Three Violent People (1956) and Winchester '73 (1967). He was part of the all-star cast in The Longest Day (1962), a film of the World War II generation, credited with saving 20th Century Fox Studios, after the disaster of Cleopatra. He considered his best role to be in In Harm's Way (1965), which is also regarded as one of the better films about World War II.
While filming the title role in The Cardinal (1962), Tom suffered from Otto Preminger's Teutonic directing style and became physically ill. Nevertheless, Tom was nominated for a Golden Globe award in 1963. He appeared with Marilyn Monroe in her final film, Something's Got to Give (1962), but the studio fired Monroe after three weeks, and the film was never finished. That experience, along with the Cardinal ordeal, left Tom wary of studio games and weary at waiting around for the phone to ring.
After viewing the film Rosemary's Baby (1968), Tom was inspired to write his own horror novel, and in 1971 Alfred Knopf published The Other. It became an instant bestseller and was turned into a movie in 1972, which Tom wrote and produced. Thereafter, despite occasional film and TV offers, Tom gave up acting to write fiction full-time. This he did eight to ten hours a day, with pencil, on legal-sized yellow tablets. Years later, he graduated to an IBM Selectric.
The Other was followed by Lady (1975), which concerns the friendship between an eight-year-old boy and a mysterious widow in 1930s New England. His book Crowned Heads became an inspiration for the Billy Wilder film Fedora (1978), and a miniseries with Bette Davis was made from his novel Harvest Home (1978). All That Glitters (1986), a quintette of stories about thinly disguised Hollywood greats and near-greats followed. Night of the Moonbow (1989), tells of a boy driven to violence by the constant harassment he endures at a summer camp. Night Magic, about an urban street magician with wondrous powers, written shortly before his death in 1991, was posthumously published in 1995. The dust jackets and end papers of Tom's books, about which he took unusual care, are excellent examples of his gifts as an artist and graphic designer, further testimony to the breadth of his talents.