Markwell is probably best recognized for having appeared as IMF agent Casey Randall in the 1988–1989 season of Mission: Impossible,[2] playing the only IMF agent in a Mission: Impossible TV series and its revival to ever be caught, killed, and disavowed.
Markwell got her first taste of acting while modeling for Plaza Three, a premiere talent agency in Phoenix during the late 1970s and early 1980s.
Early in her last episode, "The Fortune", the character was captured and killed by lethal injection during a solo assignment.
After Mission: Impossible, Markwell made guest appearances in the TV-series The Client (1995–1996), Sliders (1996–1997) and The Burning Zone (1996–1997).
In film, Markwell appeared in Stones of Death (1988), Murder 101 (1991), Robo Warriors (1996) and Jane Street (1996) and had minor parts in Grievous Bodily Harm (1988), Red Wind (1991) and The Man Who Wouldn't Die (1994).