A cool blonde beauty who played several effective lead and character roles in the 1980s, Shaver was outstanding as a prim East Coast college professor who makes a wary, but liberating foray into lesbianism in Donna Deitch's moving "Desert Hearts" (1985). She was certainly seen by a wider audience opposite Paul Newman in "The Color of Money" (1986). Shaver exudes enthusiasm in every role. She made her film debut in "Shoot" in 1976, but made a greater impact as the wife in the poltergeist-infested home in "The Amityville Horror" (1979), at the time the highest grossing independent film in history. She is also remembered as the woman "cured" by philandering Tom Berrenger in "In Praise of Older Women" (1978), the Protestant missionary in "Dr. Bethune" (1993) and as the mother of a teenage witch (Fairuza Balk) in "The Craft" (1996).
Although Shaver had made some appearances on US TV in the late 70s, she first received notice as Beau Bridges' wife in "United States", the short-lived 1980 NBC series by Larry Gelbart that closely examined a marriage. In 1981, she headlined "Jessica Novak" (NBC), about an on-camera reporter, and returned to the genre as news anchor Kelby Robinson in "WIOU" (CBS, 1990). She also made several recurring appearances during the 1982 season of "Hill Street Blues" (NBC) and has often starred in TV-movies of popular entertainment value, including the USA Network thriller "Survive the Night" (1993) and as Monique Dressier in several of the "Janek" series of CBS TV-movies. Shaver returned to series TV as psychiatrist Dr. Rachel Corrigan who becomes impregnated by a demon and gives birth to evil in the Showtime series "Poltergeist" (1996- ).
Shaver began her career as a theater actress in her native Canada, but since she began the US phase of her career, she has made infrequent stage appearances. Her work in "Ghost on Fire" at the La Jolla Playhouse was much applauded and she made her Broadway debut in Neil Simon's "Jake's Women", opposite Alan Alda. As Maggie, Jake's humorless second wife, Shaver earned a Theatre World Award.