Until his death at 74 from a heart attack, Liam Sullivan was a very busy actor on television and in theater, and in the former medium, he made a career specializing almost exclusively in erudite villains (or, at least, luckless ambitious men). A native of Jacksonville, IL, Sullivan was descended from W.E. Sullivan, the founder of the renowned Eli Bridge Company; the latter conpany became famous for popularizing the Ferris wheel, and a century later remains a mainstay of the amusement ride industry. Liam Sullivan, however, decided to go into a different end of the entertainment field, acting in local theater while attending Illinois College and later studying drama at Harvard University. His patrician good looks and dashing persona, coupled with a good range, enabled him to take a large variety of parts: playboys, rogues, heroes. In his younger days, he'd have made a perfect Rupert of Hentzau in The Prisoner of Zenda. Sullivan's Broadway credits included The Constant Wife with Katherine Cornell, and Love's Labours Lost, both in the early 1950s; and, in the 1960s, Mike Nichols' production of The Little Foxes. Though he also did theatrical work in Los Angeles, Sullivan didn't make too many movie appearances: Disney's That Darn Cat (as Agent Sullivan, no less) and Bert I. Gordon's The Magic Sword were probably his two most widely seen films.
His television career, however, which began at the start of the 1950s on live shows such as Lights Out, afforded Sullivan a busy career across four decades. He was on the soap opera General Hospital, but was also a familiar figure in prime-time series, including westerns such as Have Gun Will Travel, The Virginian, Bonanza, and The Monroes (a series in which he had a regular role as a villain); but also in science fiction (Lost In Space), crime dramas (The Fugitive, Dragnet), and comedies (Gomer Pyle, USMC). On Voyage to the Bottom of the Sea, in the episode "Leviathan," he plays an ambitious scientist whose undersea discovery results in his undergoing a hideous transformation and a horrible fate; in the Star Trek episode "Plato's Stepchildren," he made a memorable impression as a humanoid alien (working opposite Barbara Babcock in a sadistic role), glib-tongued, erudite, and perfectly at ease manipulating and attempting to kill people with his telekinetic power. He also starred in one of the more widely remembered Twilight Zone shows, "The Silence," playing a man who accepts a bet from a social rival that he can go for a year without uttering a single word. Sullivan's best performance, however, was in the 1968 Dragnet episode "The Big Prophet," as William Bentley, an academic-turned-guru (obviously inspired by Timothy Leary) whose public espousal of drug use results in a confrontation with the police. Sullivan was at his most waspish (in a manner reminiscent of Clifton Webb's Waldo Lydecker from Laura) in the three-man drama, made up entirely of his verbal sparring with series stars Jack Webb and Harry Morgan. He was still working regularly in the 1990s, right up to the time of his death, a month before his 75th birthday.