Jack was still protesting when, having left the Volks in the parking lot on the north shore, they were approaching the threemetre-high Stelco fence that blocked access to the rock; the National Park Service had put up the fence because “foolish and unscrupulous” tourists had written their names alongside those of the emigrants.

“Théo wouldn’t have done that,” said the man.

“Of course not,” she said.

But they had already stuck their noses through the wire mesh and were trying to decipher the names and dates that were half obliterated by time.

Most of the inscriptions were later than 1850. The names were those of adventurers who had gone to California in search of gold. They also found inscriptions from the 1840s, among which they recognized, with pounding hearts, some of the men and women they had got to know from reading excerpts from their diaries, whom they had come to consider almost as friends and travelling companions.

They walked slowly along the fence. When they reached the other end the girl had to acknowledge that Théo’s name was not there.

She thought for a moment.

“The Oregon Trail went along the south side,” she said.

“Where are you going?” he asked, but she had already left; her stride was determined, and she wasn’t even looking out for rattlesnakes.

The fence ended at the Sweetwater, and the river, though narrow here, formed enough of an obstacle to prevent visitors from getting to the south side. Undaunted, the girl climbed the fence and circled the rock. The man did the same, but more slowly, watching where he stepped because their favourite book said: “Be most alert for rattlesnakes in the weeds at the base of the rock.”

She had already peered at a good portion of the south face when he caught up with her.

“Come look!” she exclaimed.

From the south side, the rock resembled the shell of an enormous turtle. La Grande Sauterelle was perched on the highest part, and far above his head the man could make out vultures soaring in the sky. But he couldn’t see what she was pointing to at her feet.

“What is it?” he asked.

“Come here!” she exclaimed. “Otherwise you’ll think I’m not telling the truth.”

It was noon and it was hot. The man grumbled as he climbed the rock — truth, truth, what is the truth? — and when he reached the summit, he saw, between the girl’s widespread feet, an inscription in red:

THÉO. 75

The truth was as red as a bloodstain.

As he did every time something important happened, Jack fell silent. He couldn’t speak until they were back at the Volks, in the parking lot.

“It just says 75,” he observed. “There’s nothing to prove it was 1975. It could just as well have been 1875.”