Born in 1945 in Evansville, Indiana, Glass was an alumnus of the University of Evansville and began his acting career with regional stage roles in the 1960s. He made his television debut in the early 1970s, appearing as a guest on shows including Sandford and Son, Hawaii Five-O, All in the Family, The Bob Newhart Show, and Good Times among many others.

In 1975, he landed the first of two roles for which he would be best remembered, Barney Miller‘s Detective Ron Harris. A literary, preoccupied aspiring writer, Harris was a mainstay of the series throughout its entire eight season run, the center of an ongoing arc in which he attempted to kick off his writing career, eventually succeeding with a memoir called “Blood on the Badge”. The success would come with a price however, as ambulance-chasing lawyer Arnold Ripner would sue him for his depiction in “Blood”, receiving a huge payout late in the show’s run.

Following Barney Miller, Glass starred alongside Demond Wilson in the short-lived The New Odd Couple, appeared as Satan on a memorable episode of the 1980s Twilight Zone revival alongside Sherman Hemsley, along with numerous other guest spots including Family Matters and Star Trek Voyager, and co-starred in the short-lived sitcom Rhythm and Blues. Glass also voiced the character Randy Carmichael on the Nickelodeon series All Grown Up! and Rugrats, and lent his voice to the video game Fable II.

In 2002, Glass landed his second iconic role, co-starring on Fox’s ensemble sci-fi western series Firefly as Shepherd Book. A spiritual leader of sorts to the rag-tag crew of the space ship Serenity, Book attempted to guide them toward their better instincts while appearing to atone for a mysterious and possibly checkered past. He reprised the role for the sequel film, 2005’s Serenity, in which Book, along with Alan Tudyk’s Hoban “Wash” Washburne, were killed in what would become the quintessential examples of creator Joss Whedon’s penchant for killing off beloved characters. The character remains one of the series’ most beloved.

As Shepherd Book, Glass delivered a quiet, spiritual demeanor that reflected his own life, as he was a practicing Buddhist and a longstanding member of Soka Gakkai International, the world’s largest organization for Buddhist laity. He never married.