Laine's relationship with the musical theatre started in Britain and continued in the United States with starring performances in Sondheim's "A Little Night Music" and Franz Lehár's "The Merry Widow" (Michigan Opera). In 1980 she starred in "Colette", a musical by Dankworth. The show began at the Stables theatre, Wavendon, in 1979 and transferred to the Comedy Theatre, London, in September 1980. In 1985 she originated the role of Princess Puffer in the Broadway musical "The Mystery of Edwin Drood", for which she received a Tony nomination. In 1989 she received the Los Angeles critics' acclaim for her portrayal of the Witch in Sondheim's "Into the Woods".