[3] She is also noted for largely abandoning her acting career after the death of her sister Marguerite in the London Blitz to devote herself to helping wounded servicemen and children displaced or maimed by the war.

[7] Carroll's father opposed her taking up acting, but with her mother’s support she quit teaching and traveled to London to look for stage work.

[8] She had won a beauty contest, and got a job in Seymour Hicks' touring company, making her stage debut in 1927 in The Lash.

The following year she made her screen debut in The Guns of Loos, and then starred alongside Miles Mander in The First Born, written by Alma Reville.

On stage, Carroll appeared in The Roof (1929) for Basil Dean,[11] The Constant Nymph, Mr Pickwick (opposite Charles Laughton) and an adaptation of Beau Geste.

Carroll attracted the attention of Alfred Hitchcock and in 1935 starred as the director's earliest prototypical cool, glib, intelligent blonde in The 39 Steps.

[16]The filmmaker and actor Orson Welles called the film a "masterpiece" and screenwriter Robert Towne remarked, "It's not much of an exaggeration to say that all contemporary escapist entertainment begins with The 39 Steps.

[18] Following on from this success Hitchcock wanted to re-team Carroll with her 39 Steps co-star Robert Donat the following year in Secret Agent, a spy thriller based on a work by W. Somerset Maugham.

She followed this with The General Died at Dawn (1936), and was borrowed by 20th Century Fox to play the female lead in Lloyd's of London (1936) which made a star of Tyrone Power.

Carroll went to Columbia for It's All Yours (1937) then was cast by David O. Selznick as Ronald Colman's love interest in the 1937 box-office success The Prisoner of Zenda.

[19]: 252 In 1948 she made her debut on Broadway as Agatha Reed in Fay Kanin's Goodbye, My Fancy; a role later portrayed by Joan Crawford in the 1951 film adaptation.

[24] Her story is one of rare courage and dedication when at the height of her success she gave up her acting career during World War II to work in the line of fire on troop trains for the Red Cross in Italy after her sister was killed by a German air raid – for which she was awarded the American Medal of Freedom.

After her only sister, Marguerite, was killed in World War II's London Blitz, Carroll made a radical shift from acting to working in field hospitals as a Red Cross nurse.

[27][28] During the war, Carroll donated another property of hers, a château she owned outside Paris, to house more than one hundred and fifty orphans, arranging for groups of young people in California to knit clothing for them.

Allied Commander Dwight Eisenhower remarked in private that, of all the movie stars he met in Europe during the war, he was most impressed with Carroll and Herbert Marshall (who worked with military amputees).

[29] After the war, Carroll stayed in Europe where she conducted a radio program fostering French-American friendship and helped in the rehabilitation of concentration camp victims, during which she met her future third husband, the French producer Henri Lavorel.

[30] On her return to Paris, she and Lavorel formed a production company and made several two-reel documentaries to promote peace, one of which, Children's Republic, was shown at the Cannes Film Festival.

Carroll told The Christian Science Monitor that "wars are started at the top but can be prevented at the bottom, if all men and women will rid themselves of distrust and suspicion of that which is foreign.

"[31] Filmed in a small orphanage in the town of Sèvres, just southwest of Paris, it focused attention on the devastation of children's lives in Europe caused by war.

[8] Carroll died on 2 October 1987, aged 81, in Marbella, Spain, from pancreatic cancer and is buried in the cemetery of Sant Antoni de Calonge in Catalonia.