David J. du Plessis (1905–87) was a South African Apostolic Faith Mission pastor who is chiefly remembered for his advocacy of the Pentecostal message and experience in mainline ecumenical circles – initially Protestant and subsequently also Roman Catholic – hence his nickname of ‘Mr Pentecost’. Ziefle's monograph is the first serious scholarly study of a figure who straddles the boundary between historic Pentecostalism and the international charismatic renewal movement of the late twentieth century. The particular focus of the book is on du Plessis's tortuous relationship with the Assemblies of God in the United States. Admitted to the accredited list of Assemblies of God ministers in 1937, over ten years before he finally settled in the USA, du Plessis from the early 1950s established contact with leaders of the Protestant mainline, in part through the enthusiastic mediation of John A. Mackay, former missionary to Peru and notable Scottish president of Princeton Theological Seminary. Du Plessis's growing involvement in the official ecumenical movement stretched to the limit the patience of the fundamentalist leadership of the Assemblies of God, which in September 1962 terminated du Plessis's accreditation and reaffirmed its principled opposition to the imagined goal of the World Council of Churches to create ‘a World Super Church, which probably will culminate in the Scarlet Woman or Religious Babylon of Revelation’. Not until 1980, when the evidence of the charismatic movement's widespread penetration of the historic denominations had become undeniable, did the Assemblies of God readmit du Plessis to the fold. The extreme nature of the Pentecostal denomination's reaction to du Plessis's ecumenical advocacy has been widely attributed to its affiliation from the late 1940s with the newly formed National Association of Evangelicals and its desire to be counted as authentically ‘evangelical’. However, Ziefle plausibly argues that the divergence between du Plessis and his adopted denomination had more to do with the Assemblies of God's suspicion of any claim to the Spirit's leading that threatened its increasingly routinised understanding of charisma. For those interested in the history of Pentecostal movements, this book is a revealing exposé of the rapidity with which a movement that was founded on the unbridled activity of the Spirit hardened into institutional self-absorption and pragmatism. For those interested in the history of ecumenism, Ziefle provides a salutary reminder of how deeply entrenched were American conservative fears of the World Council of Churches, even before its theological reorientation towards humanisation and liberation from the mid-1960s. Ziefle writes from an insider perspective within American Pentecostalism, and one weakness of the book is its repeated assumption – which is likely to strike British readers as particularly odd – that the charismatic renewal of the 1960s and 1970s is a largely forgotten episode with little relevance to the ecumenical movement today. Another flaw of the book is its poor standard of proofreading. Although this book sets itself limited objectives, it achieves them quite successfully, quarrying a rich selection of archival resources, notably the du Plessis papers at Fuller Theological Seminary.