Noel Coward begged an ambitious mother: ''Don't put your daughter on the stage, Mrs. Worthington.'' Such good advice. It should be taken to heart by parents with another kind of dream who think of grooming their child for the secret service, where so many jobs manage, unlikely as it seems, to be both tedious and dangerous. Risking one's life to report on the state of highways is not everyone's idea of glamour.
But for Mary Bancroft, it was different.
Her job was certainly not boring and, compared to, say, the women who worked in the underground, wasn't hair-raisingly dangerous. Make no mistake though, it wasn't exactly safe either, as her memoir ''Autobiography of a Spy'' (William Morrow & Company, 320 pp. $15.95) makes clear. To be an active anti-Nazi was no job for the chicken-hearted.
Her trips across the frontier were infrequent, but as a highly intelligent and obviously charming American living in Switzerland married to a Swiss national, she was able to win the trust of German double agents as well as ordinary European business people crossing and recrossing the border into Nazi-dominated countries. Stories, rumors, and sights glimpsed from a train were fitted into the picture by her friend and boss Allen Dulles, head of the Swiss division of the Office of Strategic Services (OSS), who was assembling information on conditions in occupied Europe.
Perhaps the most important job Dulles assigned her was to win the confidence of Hans Bernd Gisevius, a German intelligence officer attached to the German Embassy in Switzerland. This man claimed to be planning Hitler's assassination, but was he really? He could be a double agent. Would Mary Bancroft work with him on the book he had written about the Third Reich and, while doing so, get to know him and how trustworthy he was? She succeeded beyond all expectations, giving Dulles, and now us, an inside story of the coup d'etat that, largely because of pettiness and poor planning, was a tragic failure before it even began. A conspiracy of Hamlets.
Now that story has all the glamour expected from a book with the word ''spy'' in its title. It makes fascinating reading.
But I found the story of her growing up in Cambridge, Mass., equally absorbing. Her grandmother called her ''Precious Doll,'' a misnomer if ever I heard one, for Mary liked to spend her days discussing the news of the day with the family coachmen and the local cops. ''To be told something was dangerous sent me rushing off to do it,'' she says - an ideal attitude for an embryo spy.
One of the great influences on Mary Bancroft's life was Clarence W. Barron, publisher of the Wall Street Journal and, improbable as it sounds, her stepmother's stepfather. He gave her a piece of advice that couldn't have been improved on if he had known what career she would end up in.
''Never hesitate,'' he wrote her, ''to meet people from all walks of life - even gamblers and crooks - always study them and learn to differentiate clearly between the good and bad you find everywhere, not only among people, but within individuals themselves.''
Actually this book has plenty of counsel for the young spy-in-training. Take for instance this bit of tested wisdom:
''. . . In order to engage in intelligence work successfully, it was essential to have a very clear-cut idea of your own moral values, so that if you were forced by necessity to break them, you were fully conscious of what you were doing and why.''
''I must never have any dealings with an enemy of whatever nationality whom I could not imagine liking as an individual if there had not been a war on. . . .'' Otherwise, she said, ''my judgment of the information I was receiving might be clouded. . . .''
On second thoughts, it isn't only incipient spies who can benefit from her experiences. Mrs. Worthington's daughter, on or off the stage, might find it useful. As for me, Mary Bancroft had something important to say about panicking:
When it looked as if the Nazis might invade Switzerland, she decided that to run was the most dangerous thing to do. ''Having been caught in a wave of collective panic, I realized how destructive such an experience could be. . . . Wasn't it better to stay put, face up to whatever came, and trust a bit in God rather than try blindly to escape, escape, escape, from you knew not what?''