The key phrase in the letters of St Paul in general and the letter to the Ephesians in particular is the phrase "In Him." It is repeated 164 times in the letter of St Paul, along with its synonyms like "in Christ," "in the Beloved,". In the first two chapters of the letter to the Ephesians alone, it is repeated 22 times. It is a theme that summarises God's purpose for us, His creation, from before the foundation of the world (Eph 1:4) until everything is gathered under one head, in Christ (Eph 1: 10), Saint Paul refers to this plan as "the mystery of Christ." This book will explore what this "Mystery of Christ" is and how being in Christ Jesus transforms our identity and how we live our lives. This book is a translation of a number of lectures delivered in St Macarious monastery, in the desert of Egypt, between 1987 and 1989 to the residing monks. It is an in-depth exploration of the book of Ephesians written by Saint Paul. The lectures bring the book of Ephesians to life by explaining context, examining key verses and connects Saint Paul's message to the Ephesians with the message in the Gospels, Saint Paul's other letters and sayings from the Church fathers throughout, giving the reader a cohesive understanding of Saint Paul's intentions whilst drawing to the significance of the Gospels.