The crisis came to a head not in a meeting or a laboratory, but in the cavernous, high-ceilinged assembly building they called the "Barn." The first full-scale, non-nuclear test model of the implosion device—the "Christy Gadget," named after its designer—was being assembled. It was a sinister-looking sphere of high explosives, wiring, and lenses, a polished, geometric fruit of immense destructive potential.
Robert's role was to oversee the integration of the firing unit, the complex nest of capacitors and switches that had been his domain for months. His heart was a cold, hard stone in his chest. This was no longer a test component; this was a rehearsal for the real thing. Every wire he connected, every solder joint he inspected, felt like a betrayal of everything he was.
He was working alongside Sarah, connecting the final krytron switches. The air was thick with tension and the smell of explosives and ozone.
"It's actually beautiful, in a terrifying way," Sarah murmured, wiping sweat from her brow with the back of her hand. "To think this little package could… you know."
"Yeah," Robert said, his voice hollow. "To think."
He had a decision to make. A final, irrevocable one. He had spent over a year planting seeds of delay, but the harvest was upon them. The test at the Trinity site was scheduled for just a few weeks away. If this assembly went smoothly, the timeline would be locked in.
His eyes fell on the central cavity where the plutonium core would be inserted. He knew the precise tolerance for the spherical fit. He knew that the team, based on his own earlier, deliberately conservative calculations, was planning to machine the core to a specific diameter. But he also knew, from the future, that those calculations had a tiny, cumulative error. The core they were preparing was a fraction of a millimeter too large. It would fit, but it would be tight, creating a minute asymmetry in the implosion. In the real test, it would contribute to a yield significantly lower than predicted—a 21-kiloton explosion instead of the anticipated 25.
It was a flaw he had introduced. A small one, but a flaw nonetheless. It was his last, lingering act of sabotage.
But as he looked at the device, at the focused, hopeful faces of his colleagues, the weight of his secret became unbearable. This wasn't a game. The lives of the soldiers in the Pacific, the fate of the war, the very real people in the target cities—it all crashed down on him. His interference wasn't noble; it was the ultimate arrogance. He was a single man, presuming to know the "correct" path of history.
He felt a hand on his shoulder. It was Frank, the group leader. His face was grim.
"Robert," Frank said quietly, pulling him aside. "We've got a problem. The metrology team just finished the final checks on the core mock-up. The diameter is off. It's too big."
Robert's blood ran cold. They had found it. His sabotage.
"It's within the tolerance we discussed," Robert said, his mouth dry.
"Barely," Frank replied, his eyes narrowed. "But it's on the very edge. And when I traced the tolerance back, it leads to your stress analysis from three months ago. The one where you factored in a 'theoretical thermal expansion coefficient' that was… well, it was higher than anyone else's models suggested." He paused, his gaze intense and deeply disappointed. "We based the machining specs on your numbers, Robert. Why would you do that?"
This was it. The moment of exposure. Not as a time traveler, but as a saboteur. He could see the suspicion hardening in Frank's eyes. All the "bad luck," the "eccentricities," the moments of inexplicable hesitation were now coalescing into a single, damning picture.
Before Robert could formulate a lie, a voice cut through the din of the Barn.
"That's because he's been playing us all for fools."
John Albright stood at the entrance to their work area, his grey suit immaculate amidst the grime and chaos. He must have just arrived on the mesa. His pale eyes were like chips of ice, fixed on Robert. In his hand, he held a file folder.
"Frank, could you give us a moment?" Albright's tone was polite but left no room for refusal. Frank, looking confused and angry, nodded and moved away, shooting Robert a last, betrayed glance.
Albright walked forward, stopping a few feet from Robert. He didn't raise his voice.
"I never stopped watching you, Robert," he said, opening the folder. "The flawed calculations. The brilliant solutions to peripheral problems, coupled with inexplicable errors on critical path items. The way you looked at that recruitment office in Oak Creek. The sheer, impossible breadth of your knowledge, from radios to radiology." He pulled out a single sheet of paper. It was Robert's student ID, the one he had hidden under his mattress a lifetime ago. "We did a more thorough search of Henderson's property after you left. We found this. The plastic. The photograph. The date. It's impossible. A forgery, perhaps, but to what end?"
He looked from the ID to Robert's face, his expression one of cold, final triumph.
"You're not just a saboteur, are you? You're not a spy. You're something else entirely. Something that shouldn't exist." He took a step closer, his voice dropping to a venomous whisper. "Who are you? And what have you done to my project?"
Robert stood there, surrounded by the bomb he had tried to delay, confronted by the man who had been his shadow since the beginning. The game was up. The unraveling was complete. There were no more lies to tell, no more roles to play. He was caught between the past he had tried to change and the future that had now caught up with him.
He looked Albright in the eye, all pretense gone, leaving only a vast, weary truth.
"I haven't done anything to your project, Mr. Albright," Robert said, his voice eerily calm. "You've done it to yourselves. I was just… a tourist. And I've seen how this story ends."