The book looks into the liturgy of the Mar Thoma Church. The Mar Thoma Church claims to be eastern and reformed. An enquiry is made into the liturgy of the passion week and the Eucharist to look into the theology of Atonement (work of Christ) and the nature of the Holy Spirit respectively. The measuring rod to determine the Eastern and the Reformed nature is the Eastern Fathers such as Gregory Nazianzen, Athanasius, St. Basil, etc., and the Reformer John Calvin. The theology of atonement (work of Christ) and the nature of the Holy Spirit as laid out in the liturgy of the Mar Thoma Church are compared to the teachings of the Eastern Fathers and Reformer John Calvin. Some observations are made and accordingly conclusions are drawn. Based on the conclusions some implications are made for the Mar Thoma Church. Abraham Kuruvilla is priest with the Mar Thoma Syrian Church. He completed his BD from Mar Thoma Theological Seminary, Kerala, India, and ThM from Princeton Theological Seminary, USA. He is presently serving in Philadelphia as a parish priest.