He was a veteran character actor who often played "heavies" in films like White Heat. Also played Joan Crawford's agent in the campfest Torch Song and was busted on a "morals charge" back in the day. She played Dennis's grandma on Dennis the Menace:
Mulqueen met Paul Guilfoyle in the 1920s when both were acting in New York, attending the same parties, and running around with the same theater crowd. They became "Broadway buddies."
At the age of thirty, and still a maiden lady, Mulqueen "became increasingly uncomfortable at her family's concern abort her 'unnaturally' long-term friendship with Hazel Dawn." Her adopted son, Kaier Curtin believes pressure from her father partly motivated Mulqueen impulsively to elope with John Henry Hewlett (1905–1968), a reporter from the New York Times..."On that disastrous honeymoon," Mulqueen confessed to her foster son, "I realized immediately that I had made an error in judgement and soon shipped myself off to Cuba to obtain a quickie divorce."
Her sudden divorce may have "made her Catholic family even more suspicious about her sexual predilection, so Kathleen decided to marry her longtime, social 'beard' and good time Broadway buddy, Paul Guilfoyle." She was well aware that Guilfoyle "had been sexually involved with a series of gay lovers but naively believed that he would change and settle down, perhaps even become celibate and satisfied enough, as she would be, with a compatible 'marriage of true minds'."
Hazel Dawn, who was living in retirement in Beverly Hills after a successful film career, encouraged Mulqueen and Guilfoyle to move to Hollywood...The couple moved to Los Angeles in 1935. Guilfoyle fortunately secured a longterm contract at RKO Studios, where he made some twenty-five films over the next fifteen years. In the 1950s, he directed more then 150 television shows, including episodes of Highway Patrol and Sea Hunt. But by the late 1930s, he had become an alcoholic, in part, perhaps, because be was leading a double life; he was secretly an active homosexual but publicly a married man. Also he suffered from depression over the birth of his and Kathleen's child, Anthony (1936–1988), who was afflicted with Down syndrome. He joined Alcoholics Anonymous, where he met and became friends with other Hollywood actors, all of whom helped each other to remain sober.
Kathleen, aware of her husband's sexual adventures, "was worried sick that he might be arrested." Los Angeles "was a hotbed of homophobic entrapment before, during, and after World War II," and Guilfoyle was caught in the late 1940s in a police dragnet operation...his arrest appeared on the from page of the Los Angeles Times. Both Guilfoyle and Mulqueen withdrew socially in humiliation..."What saved Kathleen's sanity during the long period when Paul was unemployable was an unexpected chance to resume her acting career with a bit part in the film Marty." Thereafter, she was cast in numerous small character roles in films and on television
At the end of the 1950s, Guilfoyle was again entrapped in a compromising situation. This time he was blackmailed. Afraid to even tell his wife, rather than resorting to his old habit of alcohol...he became addicted to codeine. He became irrational and unpredictable and so distressed his son Anthony, that Kathleen insisted that he move out of the house...in June 1961 he committed suicide. Mulqueen "never again spoke of Paul Guilfoyle, either in bitterness or compassion" until the AIDS epidemic hit in 1981-82. "Thank God, he's not alive," she said. "He'd be one of the first to come down with it."