Karlen's first acting experiences were on early television productions such as
From These Roots and
Kraft Television Theatre. His Broadway stage career began in 1959 in
Sweet Bird of Youth. He accumulated roles on both stage and television before winning one of his signature roles in 1967 in the daytime serial
Dark Shadows. It was Karlen's pivotal character of
Willie Loomis who released vampire
Barnabas Collins from his coffin, setting off the events of the series. Karlen would stay with the television series for 182 episodes, playing various characters through 1971. In addition to Willie, he played Carl Collins, a parallel-universe William H. Loomis, Desmond Collins and Kendrick Young. In the 1971 film
Night of Dark Shadows, he played Alex Jenkins along with other cast members from the
Dark Shadows TV show. While not appearing on
Dark Shadows in the late sixties, he appeared on
Love Is a Many Splendored Thing as Jock Porter and
Hidden Faces as Sharkey Primrose. He reunited with his
Dark Shadows co-stars for the 1970
House of Dark Shadows as Willie Loomis, and, in 1971, with
Night of Dark Shadows as Alex Jenkins. From 2006 to 2019, Karlen reprised the role of Loomis for a series of
Dark Shadows audio dramas produced by
Big Finish Productions. Karlen moved to a series of guest appearances on television productions, establishing himself in 1982 as Harvey Lacey Sr., husband of
Tyne Daly's character Mary Beth Lacey on
Cagney & Lacey. He appeared in 110 episodes over six years. Karlen won an
Emmy Award for his portrayal of Harvey Lacey Sr. in 1986; he received 2 further nominations, in 1985 and 1987. His career included numerous movie roles, during which he reprised the Harvey Lacey Sr. character in four
Cagney and Lacey television movies:
Cagney & Lacey: The Return in 1994,
Cagney & Lacey: Together Again and
Cagney & Lacey: The View Through the Glass Ceiling in 1995, and
Cagney & Lacey: True Convictions in 1996. ==Personal life and death==