The following material is based on an uncopyrighted text from a booklet published by the Benedictine Nuns of Perpetual Adoration in the United States. The Structure of the Mass: The first part of the Mass is a kind of introductory service, made up of chants, prayers and lessons (i.e. readings from Holy Scripture).... This first part of the Mass is called  the Mass of the Catechumens, while the remaining part is called the Mass of the Faithful. These names have their origin in the discipline of the early Church. In the first ages of Christianity, persons desiring to  become Christians were obliged to undergo a course of instructions preparatory to baptism. They were called "catechumens," a Greek word meaning "one who is being instructed." Such persons, being not yet fully initiated in the teachings and practices of Christianity, were dismissed before the sacrificial part of the Mass commenced.  Likewise those who were undergoing a course of penance and had not yet been admitted to Communion  were ordered to leave the church at this part of the Mass. That which followed was considered too holy for the presence of notorious sinners, and too mysterious to permit those to assist who were not yet fully instructed. Only those who were baptized, -- "the Faithful" -- could take part in the actual Eucharistic Sacrifice. The Church, during the course of centuries, changed her discipline in this regard, and all are now permitted to remain  during the entire sacred rite.  The Mass is not a series of acts loosely joined together; the Mass is one continuous action, reproducing in a mysterious way the Life, Passion and Death of Jesus Christ. The subdivisions of the parts of the Mass are intended only as an aid in studying the Mass. They are as follows: -- The Preparation -- which includes the prayers at the foot of the altar, the Introit, Kyrie and Gloria. The Instruction -- which includes the Collect, the Epistle, Gradual, Alleluia, (or Tract, and on certain feasts the Sequence), the Gospel (usually followed by a sermon), and the Credo. The Oblation -- which includes the Offertory antiphon, the offering of bread, the pouring of water and wine into the chalice, the offering of the chalice, the washing of the hands, the prayer to the Blessed Trinity, the "Orate fratres" and the Secret. The Consecration -- which includes the Preface and the Canon of the Mass, embracing the prayer "Te igitur," the Memento of the living, the Communicantes and the other two prayers before the Consecration and Elevation, the three prayers after the Consecration, the Commemoration for the Dead, the "Nobis quoque peccatoribus" and the Minor Elevation. (This part is, properly speaking, also a part of the oblation or sacrifice offering.) The Communion -- which includes the Pater Noster, the Libera, the Agnus Dei, the three prayers before the Communion, the "Domine non sum dignus," and the Communion of the Priest and the Faithful. The Thanksgiving--which includes the Communion antiphon, the Post- communion prayer, the "Ite missa est," ["the mass is ended"] and the Last Gospel. Some critics have seen "The Sisters" to be structured as an analogue to the Mass where what is missing is the resurrected spirit, the consecration--as under Fr. Flynn's care the Chalice (holding the consecrated wine and water) fell to earth and so instantly, according to doctrine, the liquids became merely wine and merely water again.  The Priest, of course, is also missing from the story.  To quote from Bob Dylan's Lily, Rosemary and the Jack of Hearts he's "the only person on the scene missing".  Critics who see an analogy to the Catholic Mass, focus on the "communion scene" in the story, where the boy, his aunt, and the priest's sisters holding glasses of wine focus on the empty fireplace.