Owen Roberts was fifteen when he joined the new railway company building its narrow gauge railway among the Welsh slate quarries. Jennie arrived soon after him, and the two of them grew old together. This is a story of triumphs and troubles, successes and failures, among the Welsh hills. A story where son succeeds father, and where grandson and later great-grandson take over. A human story in which the engines that pull the trains seem almost human too. First published in 1958, and written when the author was in his twenties, Jennie remains the only family saga which is based around a Welsh narrow gauge railway, and arguably the only family saga written based on a railway anywhere, and of any gauge.