Miguel received permission from his superiors to return to Mexico incognito and to carry on his ministry undercover. He slipped into Mexico City and immediately began celebrating Mass and distributing the sacraments – often under imminent threat of discovery by a police force charged with the task of ferreting out hidden pockets of Catholicism.
Miguel had many narrow escapes. Once, after celebrating Mass in a home, he received just enough warning to be able to slip out a side door before the police surrounded the place. With characteristic bravado, Pro changed into a police inspector’s uniform (one of the many disguises he made use of while eluding authorities) and went back to the very house where the police were busy hunting for him. Swaggering up to the policeman in charge, Pro demanded to know why they hadn’t yet succeeded in capturing "that rascal Pro". None the wiser, the abashed officer promised to redouble the search efforts.
Another time, Pro was in a taxi being pursued through the streets of Mexico City by several police cars. Ordering the driver to slow down as he rounded a corner, Pro rolled out of the car, lit a cigar, and began strolling arm in arm with an attractive (and startled) young woman. When the police roared by, in hot pursuit of the now Pro-less taxi, they paid no attention to the romantic young couple
on the sidewalk.
He became known throughout the city as the undercover priest who would show up in the middle of the night, dressed as a beggar or a street sweeper, to baptize infants, hear confessions, distribute Communion, or perform marriages. Several times, disguised as a policeman, he slipped unnoticed into the police headquarters itself to bring the sacraments to Catholic prisoners before their executions. Using clandestine meeting places, a wardrobe of disguises (including policeman, chauffeur, garage mechanic, farm laborer, and playboy), and coded messages to the underground Catholics who received his notes signed "Cocol," Pro carried on his priestly work for the Mexican faithful under his care.
