Adrienne von Speyr was one of the most important mystical theologians of the last century, heralded by figures like John Paul II and T.S. Eliot. However, her work has been eclipsed in many ways by her personal connection to Catholic theologian Hans Urs von Balthasar. Heaven Opens provides one of the first comprehensive accounts of von Speyr’s theology, MatthewLewis Sutton argues that the eternal, immanent relations of the Triune God ground the mystical theological vision of von Speyr. Rooted in this vision of divine love, von Speyr’s work is an account of the opening of heaven, a revelation of the Trinity’s interior life turned outward to the world, that links intimately to the sacraments, prayer, the church, and the ethical life of obedience. In von Speyr’s mystical theology, God as Triune journeys to us in order to brings into the inner life of the Trinity. Here, von Speyr’s work is for the first time given an independent hearing, expositing its content, features, and connections, and assessing its contribution to contemporary Catholic theology.