The story is told as a narrative by an unnamed veteran who participated in the Battle of Dorking. He is recounting the final days before and during the invasion of Britain. It is addressed to his grandchildren as an event fifty years earlier. Beginning sometime after an event similar to the Franco-Prussian War, concerns grow with the mobilisation of armed forces near the Netherlands. The Royal Navy is destroyed by a wonder-weapon ("fatal engines"), and an invasion force suddenly lands near Worthing, Sussex.