"We can't stop an eight-figure customer lot because one technician has a feeling," Grant said.
Ethan's expression barely changed. "Then don't stop it because of a feeling. Stop it because the timing fault is in the certified traceability chain."
Diane looked at Grant. "Quality can hold the lot."
Grant's jaw tightened. "For how long?"
"Until we know whether the reference is stable."
The hold went in at eight fourteen that evening.
Ethan stayed. He had started work earlier that day and could have left when the night crew arrived. Nobody formally ordered him to remain. That mattered later because Grant would describe the overnight effort as something Ethan had volunteered to do and therefore something that should not influence how management judged the next morning.
Voluntary work has a strange way of becoming invisible once it succeeds.
Ethan called Claire at nine twenty from the break area.
"You home?"
"Yeah."
"Door locked?"
"Dad."
"Humor me."
He heard the deadbolt click through the phone.
"Locked."
"Food's in the fridge. Pasta on the second shelf. Don't wait up."
"Again?"
"Carrington lot. Something's wrong with line four."
Claire was silent for a second. "You promised you'd be home tomorrow afternoon."
"I will be."
"You always say that when you're about to sleep at work."
Ethan smiled despite himself. "I'm not sleeping here."
"That's worse."
"Finish your scholarship essay."
"You're avoiding the subject."
"Love you too."
"Love you. Don't die in a machine."
"That's an unusually specific request."
"I've met your machines."
He ended the call with the small smile Claire could produce in him even on the worst shifts.
The next nine hours and forty minutes were the kind of work nobody photographs. Ethan, Katherine, Diane, and two technicians named Noel Briggs and Sam Patel moved backward through the system one section at a time. They pulled logs, swapped the suspected sensor, checked grounding, verified network timing, compared firmware revisions, and ran thermal cycles while the rest of the plant gradually emptied around them.
At eleven thirty, the replacement sensor produced the same intermittent fault. That eliminated the sensor itself.
At twelve forty-five, Noel found a grounding strap that looked suspicious. They replaced it. The fault returned forty minutes later.
At one twenty, Grant walked through the bay with a coffee and asked for an update.
"No root cause yet," Katherine said.
Grant looked at Ethan. "How long?"
"Still don't know."
"That's not an answer."
"It's the accurate one."
Grant's mouth tightened. "The dashboard is showing four hours of lost production."
Ethan glanced at the line. "Then the dashboard knows exactly how long we've been protecting the batch."
Diane looked down quickly to hide a smile. Grant noticed anyway.
"Get it running," he said, and walked away.
At two fifteen, Sam suggested the August vendor firmware update. Katherine loaded the revision notes and found nothing directly related to timing synchronization, but they reverted one controller anyway. The fault did not disappear.
At three ten, they had ninety clean minutes.
Noel leaned against a cabinet. "Maybe we got it."
Ethan shook his head.