The Church Dogmatics (CD) is an unfinished theological summa. Karl Barth started the Church Dogmatics in 1932, and had planned five volumes of the Church Dogmatics, but abandoned it near the end of his life in 1967, before completing the fourth volume. We possess a fragment on baptism from the final part of volume (CD IV/4) and some lecture notes on the unwritten end of CD IV; however, we possess no outlines, lecture notes, or fragments on the unwritten final volume of the Church Dogmatics, Vol 5: The Doctrine of Redemption (CD V). All we know is that the final volume on the Doctrine of Redemption would be on eschatology and the Holy Spirit, and beyond these enigmatic clues, we have only sparse comments from Karl Barth, and comments from people who knew Barth, that allow us to speculate on what CD V might have contained. John D. Godsey is one of these people, and in his Karl Barth Table Talk, recorded in the 1950's (while Barth was writing CD IV), Godsey shared some speculative evidence about the contents of the unwritten conclusion to the Church Dogmatics.
John D. Godsey on the Doctrine of Redemption
The contents of CD V is one of the greatest unsolved mysteries in the history of theology, and Godsey's following comment may be a key piece of evidence leading to solving this great unsolved mystery! We may hope and dream that an outline, interview or notebook may one day be discovered in the catacombs of the Karl Barth Archiv, or the Center for Barth Studies at Princeton, or the relics of Barth's family, friends or students that will solve this great mystery. Until that day, we may only speculate and dream for a discovery one day! And maybe quotations, like the following from Godsey, will lead to solving this unsolved mystery.
In John D. Godsey's Karl Barth's Table Talk, he describes the Church Dogmatics, Vol 5: The Doctrine of Redemption:
The Doctrine of Redemption. The final volume of the Church Dogmatics will undertake an elaboration of the Doctrine of Redemption, that is, of the activity of God that is properly appropriated to His mode of existence as Holy Spirit. It may be a surprise to some readers that man's 'redemption' is directly connected to the Holy Spirit rather than the Son. That this is theologically correct, however, has already been grounded exegetically in Volume I, Part 1. In this final section Professor Barth must discuss the Doctrine of the 'Last Things', of the Final Judgment and Consummation, of the Command of God from the viewpoint of Promise. We may expect that the Christological thread will be traced to the final page of the Church Dogmatics, that Jesus Christ, who is the Alpha, will also be the Omega! 
—John D. Godsey
[^1] Barth, Karl. Karl Barth's Table Talk. Ed. John D. Godsey. London: Oliver and Boyd, 1965. 9. Print.
Related: CD IV, CD IV/4, CD V, Doctrine of Redemp, eschatology, Holy Spirit, John D. Godsey, Karl Barth