Following small parts in Lincoln Center repertory productions, Danner landed the supporting role of Jill Tanner, the free-spirited love interest, in Leonard Gershe's new comedy Butterflies Are Free.
The play premiered Oct. 21, 1969, at the Booth Theatre. The production also marked the Broadway composing debut of a young Stephen Schwartz (credited in the Playbill as Steve), who penned the title song.
Clive Barnes of the New York Times closed his review with praise of Danner, calling her "a new young actress in the grand mannerism of Sandy Dennis, Julie Harris and all those predecessors who have made jaded, critical hearts beat a little faster...a young lady at the commencement of a big future."
Danner went on to win the 1970 Tony for Best Featured Actress in a Play. Her later Broadway credits would include Tony-nominated performances in A Streetcar Named Desire, Betrayal and Follies.