'I never saw the man again, alive or dead. One will say that I saw him only for a moment, that it was misty at the time, and that even I did not recognise the features, covered as they were with grime and stubble. Yet I am sure that the taller of the two ragged civilians I saw in the chalk quarry that misty March morning of 1918 was that Lieutenant Peter Rawley, R. F.A., who the official records stated was killed near Arras the previous autumn.'

Behind the Lines is a thriller that follows on from the success of W. F. Morris's first novel, Bretherton: Khaki or Field-Grey? Morris is again concerned with questions of identity, allegiance, chance, concealment and self-discovery. A subaltern is forced to flee when he accidentally kills an overbearing, taunting fellow officer: appearances are all against him and he does not trust to trench justice. He becomes a fugitive and has to join forces with other deserters, lost soldiers and outlaws in a hand-to-mouth existence in the no man's land between opposing forces. A series of adventures and disasters ensue, including capture by the Germans and near death by firing squad. Only his own bravery and the devotion of his fianc can rescue him from his plight.

A contemporary commentator noted that 'in spite of the flood of war books', Morris was able to achieve 'a quite different viewpoint from all the others', and his book was 'an outstanding success'.