One evening in the summer of 1868, twenty years after Sister Jovita had last been seen, Detective Masilewski was driving homeward toward Warsaw, after a day’s hunt, when an old peasant stepped before the horse, doffed his hat and asked: “Are you the secret detective, Mr. Masilewski?” On being answered affirmatively he handed the investigator a letter, explaining that an unknown man had handed it to him with a tip to pay for its delivery. The note said simply: “Dear Sir: In the convent of St. Mary of the Carmelites at Cracow, a nun by the name of Jovita, her real name being Barbara Ubrik, has been held a captive for twenty years, which imprisonment has made her a lunatic. I do not care to mention my name but vouch for the truth of my assertion. Seek and you will find. “Your correspondent.” Masilewski drove on in silence, puzzled and not a little incredulous. True, he had heard of this nun and her disappearance, but she had vanished long ago and surely death had sealed the lid of this mystery, as of others. No doubt this was another of those romantic reappearances of the famous missing. Still--what if there were truth in it. But no, it must be a figment, else why had the informant hidden himself? It was an attempt to make a fool of an honest detective. So Masilewski hesitated and waited, but the remote possibility of something grotesque and extraordinary plagued him and drove him at last to action. Even when he had determined to move, however, he knew that he must act with caution. If he were to go to the bishop of the diocese, for instance, and ask for permission to search the nunnery of St. Mary’s, the very possible result might be the transfer of the unfortunate nun to some new hiding place and the infliction of worse penalties and tortures. If he appealed to the Austrian civil authorities (Austria having annexed the province of Cracow in 1846), he might enter the convent and find himself the victim of a hoax, which is, after all, the ultimate humiliation for a detective. There was no possible course except cautious investigation. So Masilewski went to work. Carefully and slowly he traced back the stories of Barbara Ubrik’s mother, the exchanged babies, the theft by the old Jew and the captivity with the Gypsies. He discovered the record of Barbara’s parents’ marriage, got the young nun’s birth certificate, learned about her admittance to the convent, the part played in her life by Father Gratian and the early chastisement. How he did these things one needs hardly to recount, but unrelenting care and watchful judgment were necessary. He must never let the enemies of the nun know that a detective was at work. All he did had to be handled through intermediaries. Probably it would even be a thankless job, but it was an enigma, a temptation. He went ahead.