There was not much said on the journey. At four o'clock Hortense and Rénine reached Rouen. But here Rénine changed his road.
"Adolphe, take the left bank of the Seine."
He unfolded a motoring-map on his knees and, tracing the route with his finger, showed Hortense that, if you draw a line from Le Havre, or rather from Quillebeuf, where the road crosses the Seine, to Dreux, where the stolen car was found, this line passes through Routot, a market-town lying west of the forest of Brotonne:
"Now it was in the forest of Brotonne," he continued, "according to what I heard, that the second part of The Happy Princess was filmed. And the question that arises is this: having got hold of Rose Andrée, would it not occur to Dalbrèque, when passing near the forest on the Saturday night, to hide his prey there, while his two accomplices went on to Dreux and from there returned to Paris? The cave was quite near. Was he not bound to go to it? How should he do otherwise? Wasn't it while running to this cave, a few months ago, that he held in his arms, against his breast, within reach of his lips, the woman whom he loved and whom he has now conquered? By every rule of fate and logic, the adventure is being repeated all over again ... but this time in reality. Rose Andrée is a captive. There is no hope of rescue. The forest is vast and lonely. That night, or on one of the following nights, Rose Andrée must surrender ... or die."
Hortense gave a shudder:
"We shall be too late. Besides, you don't suppose that he's keeping her a prisoner?"
"Certainly not. The place I have in mind is at a cross-roads and is not a safe retreat. But we may discover some clue or other."
The shades of night were falling from the tall trees when they entered the ancient forest of Brotonne, full of Roman remains and mediaeval relics. Rénine knew the forest well and remembered that near a famous oak, known as the Wine-cask, there was a cave which must be the cave of the Happy Princess. He found it easily, switched on his electric torch, rummaged in the dark corners and brought Hortense back to the entrance:
"There's nothing inside," he said, "but here is the evidence which I was looking for. Dalbrèque was obsessed by the recollection of the film, but so was Rose Andrée. The Happy Princess had broken off the tips of the branches on the way through the forest. Rose Andrée has managed to break off some to the right of this opening, in the hope that she would be discovered as on the first occasion."
"Yes," said Hortense, "it's a proof that she has been here; but the proof is three weeks old. Since that time...."