One Shepherd, One Flock is a conversion story like no other.
For one thing, it was written before the author was received into the Church. In fact, it is a journal he kept during the year in which he was coming to a decision about whether or not he must become a Catholic.
For another, he and his wife were both Congregational ministers, very happily placed in a New England parish. Becoming a Catholic meant leaving a pleasant home, congenial work, and security. He did not know whether his wife would decide to become a Catholic too. She was attracted by the Church but was not approaching it by the same path as he was. Whether she would arrive at the same decision he could not tell. In the face of all that, what made Oliver Barres so certain he must go straight forward into the Church?
In his introduction to the book, Frank J. Sheed says of him: "He has a hunger and thirst for reality, for the objective. That a creed stimulates or consoles or quiets the conscience, that it meets one's desires or felt needs -all that is splendid, but secondary. Unless it is true, he will have none of it."