All Things Betray Thee, by Gwyn Thomas, is a novel of early industrialism in South Wales. It was first published in 1949, and was republished in 1986, with an introduction by Raymond Williams. The book was later republished as part of the series by Parthian Books in 2011. Set in 1835, this work is significantly different from most of Gwyn Thomas's work. It is both a personal story and an account of the origin of the industrialised and mostly English-speaking society of the South Wales Valleys.