A tough-looking, blond Warner Bros. starlet of the mid-'40s, Minnesota-born Peggy Knudsen made an auspicious screen debut as Mona Mars in the noir classic The Big Sleep (1946). Although a mere bit -- one scene, a couple of lines of dialogue -- the character was much discussed prior to actually appearing in the film and demanded an actress who could match the buildup. The pivotal scene, in which protagonist Humphrey Bogart finds himself at a disadvantage in gangster Eddie Mars' coastal hideaway, had originally been filmed in 1944 with Pat Clarke in the role of Mrs. Mars. But when negative previews necessitated scenes to be added or re-shot, director Howard Hawks replaced Miss Clarke with Knudsen, a much more vibrant presence who made her few moments count. It should have been a major breakthrough for the actress but Warner Bros. missed the opportunity and instead assigned her standard "other woman" roles opposite Erroll Flynn in the marital comedy Never Say Goodbye (1946) and Ronald Reagan in the horse breeding drama Stallion Road (1947). 20th Century Fox borrowed her for a couple of B-movies, in one of which, Trouble Preferred (1948), she was top-billed as a policewoman in training, but they were too inexpensive to have much impact. Missing out on stardom, she went on to appear in supporting roles through the 1950s, both in feature films and on television, retiring after a guest spot on Texas John Slaughter (1961). The victim of a crippling arthritic condition that eventually necessitated five operations, Knudsen was reportedly cared for by lifelong friend Jennifer Jones. Her death in 1980 was attributed to cancer.