Shaw's best-known film role to date was as the sympathetic therapist with whom the cerebral palsy-afflicted Christy Brown (Daniel Day-Lewis) falls unrequitedly in love in "My Left Foot" (1988). The actress has easily moved between comedy and tragedy onstage and her film performances have also captured her facility with these shifts. Shaw made her debut as a nun caring for children during World War II in "Sacred Hearts" (1984) and following her "My Left Foot" success, has shown her versatility in diverse role ranging from the free-spirited wife of explorer Sir Richard Burton (Patrick Bergin) in "Mountains on the Moon" (1990) to her scene-stealing turn as the sex-starved head of Pileforth Academy in the comedy sequel, "Three Men and a Little Lady" (1990) to a lascivious liberal in "London Kills Me" (1991). She played over-the-top villainesses in the unworthy comedies "Super Mario Bros." and "Undercover Blues" (both 1993) before essaying fine supporting turns in "Persuasion" (1995), as the sister of the heroine's true love, and "Charlotte Bronte's 'Jane Eyre'" (1996), as the dreadful aunt. Under Warner's watchful eye, she recreated her stage triumphs as "Hedda Gabler" (1993, with Stephen Rea) and "The Waste Land" (1995). Shaw once again appeared onscreen alongside Rea and newcomer Eamonn Owens as Mrs. Nugent, the bane of existence for Owens' "The Butcher Boy" (1997) in Neil Jordan's acclaimed dark comedy about a serial killer. She was wasted in support of Sean Bean and Sophie Marceau in Bernard Rose's remake of "Anna Karenina" (also 1997) and Ralph Fiennes and Uma Thurman as a senior intelligence officer in the disastrous big screen version of "The Avengers" (1998).
Shaw lent her intelligence to the role of Hedda Hopper in the acclaimed HBO movie "RKO 281" (1999), which traced the behind the scenes machinations during the making of "Citizen Kane" in 1940-41. In 2000, she appeared in the popular BBC miniseries "Gormenghast" as Irma Prunesquallor and was prominently featured in Warner's big-screen debut "The Last September" as a sophisticated Anglo-Irish woman caught up in the decline of a great house. Co-starring stage legends Maggie Smith and Michael Gambon and executive produced by Jordan, "The Last September" was well-received by critics and art-house audiences, with Shaw singled out for praise for her virtuoso performance. Just weeks after the film hit American screens the actress returned to the stage at Dublin's Abbey Theatre as the tragic heroine in another Warner-helmed project, "Medea".