On the evening before the Denver presentation, Mateo asked Lena to open the conference schedule and read the session titles. He was proud that her name appeared among the speakers, but he seemed even more interested in the problems the students were trying to solve. After she finished, he told her about his first safety assignment, when he had been too embarrassed to ask a basic question in front of senior colleagues. A patient mechanic had quietly shown him the missing detail. "Competence isn't never needing help," he said. "It's knowing what help to ask for." Lena stored the sentence away. During their journey she would see that lesson repeated in a crew asking for medical volunteers, in a captain seeking a second opinion, and in an older man allowing his granddaughter to take his arm. None of those moments diminished anyone. They made a difficult day possible.

The flight continued after the passenger was transferred to medical care. They landed in Denver late at night. Mateo was exhausted but content. At the hotel, Lena helped him arrange his medication and set an alarm for the morning.

The conference presentation went well. Lena showed the rover stopping when its sensors disagreed. The audience asked questions about reliability and human oversight. Mateo sat in the front row, wearing his old safety board pin on his lapel.

The board — the old safety board, from his years as an investigator — was the one he wore to hearings, frayed at the edges, with a pin from a conference nobody remembered, and he wore it, Lena knew, not from vanity but from habit: it was the garment he reached for when a room required him to be, at once, a grandfather and a witness. He sat in the front row, straight-backed, notebook open on his knee, and he took notes during his granddaughter's presentation the way he had taken notes during investigations — in columns, with dates — because some habits, once learned, become the way a person loves: quietly, procedurally, and completely.

Afterward, he told her that he had never been prouder of a machine that stopped. "People think progress always means going faster," he said. "Sometimes progress is knowing when not to move."

They sat together in the hotel lobby afterward, too tired to go up to the room right away. Mateo ordered hot chocolate. Lena ordered the same, though she was sixteen and felt she should want coffee. Some habits were worth keeping.

"Do you remember," Mateo said, "the first time you fixed something? Really fixed it, not just watched me?"

"The radio," Lena said. "The one with the loose antenna wire. I was nine."

"You diagnosed it before I did." He smiled into his cup. "I pretended I'd seen it too. I hadn't."

Lena laughed. "You lied to protect my feelings?"

"I lied to protect my pride." He set the cup down. "Lena, there's something I want you to know. That morning on the phone — at the airport — I was scared too."

"You didn't sound scared."

"I've had practice sounding calm." He looked at her seriously. "I want you to know that courage isn't the absence of fear. It's what you do while you're afraid. You stood at that door and asked for the record. That's the bravest thing I've ever heard anyone do."

She felt her throat tighten. "You taught me."

"I gave you the words. You chose to say them." He reached across the table and took her hand. His hand was thinner than she remembered, the veins more visible. "Whatever comes next — the conferences, the engineering, all of it — remember that the words only work if you mean them. Check the record. Ask the question. And be kind while you do it."

"I will, Grandpa."

"I know you will." He leaned back, tired but satisfied. "Now tell me about this rover of yours. I want to understand the uncertainty feature properly before I fall asleep."

So she told him — about the sensors, the pause, the human review. He asked sharp questions, the way he always did, and she answered them, and for a little while it was just the two of them at the kitchen table again, a radio with its back removed between them, the world reduced to a problem they could solve together.

Mateo died the following summer, peacefully, with Ana and Lena beside him. His funeral was small. People from his years at the safety board came to share stories about investigations he had led and reports he had written. Most remembered his patience. He was known for asking one more question after everyone else thought the answer was clear.