This study explores the way in which, by way of the Christian mysteries, divine action impacts human life. The triune God acts in Jesus Christ by means of historical events whose effects transcend time and which are mediated through their celebration in memorial and worship. Drawing on both Evangelical and Catholic writers, Nichols provides evidence that the general portrait of Jesus found in the Pauline letters and the four Gospels rests on reliable historical witness. On this basis, he offers a concise Christology which presents Jesus Christ as the fulfillment of the Messianic hope of the Old Testament; explores his unique being as laid out in the teaching of the great Ecumenical Councils of the first Christian millennium, and describes how the classic theologian of the Latin tradition, St Thomas Aquinas, sees the chief historical events of Christ’s life as affecting humanity throughout future time. Nichols then looks at the Christian concept of God – namely, Trinitarian monotheism. God so conceived can act efficaciously in the created order and does so by the deployment of his Word and Spirit in ways which express for a fallen, historical world, the dynamics of the interaction of the divine Persons in eternity – Persons who now draw human beings within their range. Those gains in understanding are then applied to the individual mysteries of the life of Christ, from his biological conception to his coming Parousia. For each mystery, Nichols describes a biblical preamble; an account of how the mystery is seen by the Liturgy and the Fathers of the Church; illumination from the three theological masters whom the author makes his own in this work – Aquinas, Balthasar and Bulgakov;- and a visual image drawn from the treasury of sacred art.