Following a year-long absence from acting (and marriage to Capt. Philip Astley of the King's Guards) she returned to the screen, having been tempted with a lucrative contract by Gaumont-British. The resulting films, Sleeping Car (1933) and I Was a Spy (1933), were both popular and critical successes and prompted renewed offers from Hollywood. However, on loan to Fox, the tedious melodrama The World Moves On (1934) did absolutely nothing for her career and she quickly returned to Britain--a fortuitous move, as it turned out. Alfred Hitchcock had been on the lookout for one of the unattainable, aloof blondes he was so partial to, whose smoldering sexuality lay hidden beneath a layer of ladylike demeanor (other Hitch favorites of that type included Grace Kelly and Kim Novak). Madeleine fitted the bill perfectly. The 39 Steps (1935), based on a novel by John Buchan, made her an international star. The process was not entirely painless, however, as Hitchcock "introduced" Madeleine to co-star Robert Donat by handcuffing them together (accounts vary as to how long, exactly, but it was likely for several hours) for "added realism". In due course the enforced companionship got the stars nicely acquainted and helped make their humorous banter in the film all the more convincing.
Hitchcock liked Madeleine and attempted to repeat the success of "The 39 Steps" with Secret Agent (1936), but with somewhat diminished results (primarily because Donat had to pull out of the project due to illness and Madeleine's chemistry with John Gielgud was not on the same level as it was with Donat). Nonetheless, her reputation was made. After Alexander Korda sold her contract, she ended up back in Hollywood with Paramount. Initially she was signed for one year (1935-36), but this was extended in 1938 with a stipulation that she make two pictures per year until the end of 1941. The studio publicity machine touted Madeleine as "the most beautiful woman in the world". This was commensurate with her being given A-grade material, beginning with The General Died at Dawn (1936), opposite Gary Cooper. For once, Madeleine portrayed something other than a regal or "squeaky clean" character, and she did so with more warmth and élan than she had displayed in her previous films. She then showed a humorous side in Irving Berlin's On the Avenue (1937); had Tyrone Power and George Sanders fight it out for her affections in Lloyd's of London (1936) (on loan to Fox); and turned up as a particularly decorative--though in regard to acting, underemployed--princess, in The Prisoner of Zenda (1937). Thereafter she had hit the peak of her profession in terms of salary, reportedly making $250,000 in 1938 alone. For the remainder of her Hollywood tenure, Madeleine co-starred three times with Fred MacMurray (the most enjoyable encounter was Honeymoon in Bali (1939)), and opposite Bob Hope in one of his most fondly remembered comedies, My Favorite Blonde (1942). Then it all started to come to an end.
Having lost her sister Guigette during a German air attack on London in October 1940, Madeleine devoted more and more of her time to the war effort, becoming entertainment director for the United Seamens Service and joining the Red Cross as a nurse under the name Madeleine Hamilton. She was unable to rekindle her popularity after the war, her last film of note being The Fan (1949), a dramatization of Oscar Wilde's play. She made a solitary, albeit very successful, attempt at Broadway, with a starring role in the comedy "Goodbye, My Fancy" (1948), directed by and co-starring a young Sam Wanamaker. There were a few more TV and radio appearances but, for all intents and purposes, her career had run its course. Britain's most glamorous export to Hollywood became increasingly self-deprecating, rejecting further overtures from producers. Instead, she became more committed to charitable works on behalf of children, orphaned or injured as the result of the Second World War.
Madeleine spent the last 21 years of her life in retirement, first in Paris, then in the south of Spain. Two of her four ex-husbands included the actor Sterling Hayden and the French director/producer Henri Lavorel. Last of the quartet was Andrew Heiskell, publisher of 'Life' magazine. She died in Marbella in October 1987. In her private life, the trimmings of stardom seemed to have mattered little to Madeleine. As to her status as a sex symbol, she was once said to have quipped to a group of collegians who had voted her the girl they'd most like to be marooned with on a desert island, that she would not object, provided at least one of them was a good obstetrician!