In this final part of the ECHO series, we see how the whole Catholic Faith comes together in a marvelous and organic unity through a life of prayer. In prayer, all of Catholic doctrine is illuminated: we discover who God is and we come to know ourselves as his beloved children; the sacraments take on their fullest meaning; our moral actions become beautifully clear. In Part IV of the ECHO series, we will discuss the essential role of prayer in the Christian life, and the way that prayer mysteriously and powerfully conforms our hearts to Christ.