She hesitated. "I think the people running the railway may have trusted a number they didn't test."
He was quiet for long enough that she wondered whether the connection had failed. Then he said, "Tell me exactly what you know, and keep the guesses in a separate pile."
She described the old float gauge, the remote sensor, and the possibility of a closed isolation valve. Tomas listened without interrupting. He had never been a structural engineer, but in thirty-one years among electrical systems he had seen too many machines made unreliable by one small disconnected component.
"A display tells you what reaches it," he said. "It does not tell you whether the world is connected to the other end."
Mina smiled in spite of herself. "That's what I thought."
"Don't confuse a good question with an answer. People who run trains need evidence and authority. Find someone who has both."
She told him about Anika and Jun. Tomas sounded relieved. He also told her something she had not known: during a storm twelve years earlier, a freight train was held at Graypine for almost six hours because a station porter had noticed brown water emerging from an old drain. The delay had cost the railway money and provoked complaints. By morning, the bank above the track had slid onto an empty section of rail.
"Did they thank the porter?" she asked.
"Not at first. He was suspended for failing to follow the approved reporting channel. They apologized after the inquiry."
"That's terrible."
"It's common enough that good organizations build better channels. But they have to use them."
After the call, Mina found Bea in the corridor and repeated only the public part of the story. Bea remembered writing about that landslide as a student intern. She showed Mina a faded article from the paper's archive. The porter, a woman named Ruth Kellan, had said that the water's color frightened her because it carried soil from inside the hillside. Mina examined the image of the ruined cutting. The place was not Rook Cut, but the lesson felt uncomfortably close.
A steward offered warm towels. The passengers at the next table were discussing whether the scheduled champagne toast would be canceled. They had heard rumors of a delay and assumed that a minor technical fault had interrupted the celebration. Mina envied their ignorance for a moment. Then she realized that she would not exchange what she knew for the ability to enjoy dessert.
Anika found her by the map. "We're stopping at Graypine for an operational review," she said. "I don't know how long."
"Are you allowed to tell me that?"
"You're a passenger. You should know why your train is delayed."
"Mr. Dane won't like it."
"He can dislike it from a safe platform."
They both smiled. Anika looked tired, and Mina could see the effort it took to keep her voice light. When she asked whether Mina wanted to speak to the driver, Anika shook her head. The driver had urgent responsibilities and the control room was not a place for visitors. But she invited Mina to help organize the public diagrams into a clear timeline, something the teenager could do without entering a restricted workspace.
Mina arranged the records across a table. The old gauge was removed in March. The new sensor was installed in April. Its commissioning note was signed in May. The pump assembly, however, did not appear on the completion list until July. She circled the gap between those dates. A gauge could have been certified months before the equipment it depended on was connected.
"Look at the revision number," Bea said.
The drawing used for the installation was Revision C. The commissioning document referred to Revision B. Someone had tested the system against an earlier design. It was not proof of wrongdoing; revisions could be recorded badly. But it was a specific question that could be answered by a specific person.
Outside, the train began to brake. Through the rain, Graypine's platform emerged from the night, with a yellow sign and a waiting bench beneath a tin roof. Mina felt the relief of slowing, then felt ashamed for the relief because someone was still outside at Mile Eighty-Four. Her grandfather's words stayed with her. Keep the guesses separate. Find someone with evidence and authority. She folded the map carefully and prepared to help the adults ask a better question.