An effervescent, square-jawed blonde performer, Plimpton made her mark playing the estranged daughter of Tommy Lee Jones in "The River Rat" (1984) and gave a fine performance as the girlfriend of River Phoenix in Sidney Lumet's "Running on Empty" (1988). Her early roles as appealing tomboys in such films as "The Goonies" (1985) and "The Mosquito Coast" (1986) were reminiscent of Jodie Foster's persona of the 1970s. After "Running on Empty", the casually attractive Plimpton played the archetypal adolescent daughter with a rebellious strain in "Parenthood" (1989) and in "Samantha" (1992). She