The Uttermost Farthing by Marie Belloc Lowndes

The fact that he was being watched had a curious effect on Laurence Vanderlyn. It roused in him the fighting instinct which he had had to keep in leash the whole of that terrible first day of repression, save during the moments when he had been confronted with the head of the detective department at the Prefecture of Police.

As at last he walked on, now choosing deliberately quiet and solitary streets, the footsteps of his unknown companion echoed loudly behind him, and he allowed himself, for the first time since the night before, the cruel luxury of recollection. For the first time, also, he forced himself to face the knowledge that any hour might bring as unexpected a development as had been the prolonged presence of Pargeter in Paris. He realised that he must, if possible, be prepared, forearmed, with the knowledge of what had occurred after he had left the darkened railway carriage at Dorgival. News travels slowly in provincial France, yet, even so, the fact that the dead body of a woman had been found in a first-class carriage of the Paris demi-rapide must soon have become known, and made its way into the local press.