Callin Reeh stood in the customs line at Singapore's Orbital Descent Terminal, watching the blur of transit pods through the transparent aluminum walls. He hadn’t expected to see those walls again. Each capsule carried its passengers down the space elevator's carbon-diamond tether, a stream of humanity flowing between Earth and stars. The sight should have filled him with wonder – it had, every other time he'd made planetfall. Today, his attention fixed instead on the chrono display above the security gate: 14:27:33 Earth Standard Time, 12 September 2487.
Four days and three hours since he'd left. Just as his ship's chronometer had shown.
Impossible.
The line shuffled forward. A child in front of him squealed in delight as a particularly fast pod streaked past, its emergency brake-jets painting orange trails against the evening sky. The child's mother – sporting the characteristic silver-white hair of a deep space navigator like himself – smiled indulgently. Neither seemed to notice anything amiss with the universe.
"Next," called the customs officer, her voice carrying the slight harmonic undertone of a vocal augment. Callin stepped forward, briefly retracting his hair for the identity scan. The officer's augmented eyes flickered with data streams as she processed his information.
Her expression didn't change, but her hand moved to the silent alarm panel.
"Sir, there seems to be a discrepancy with your departure record," she said, voice carefully neutral. "Would you mind stepping into secondary screening?"
Of course there was a discrepancy. He'd broken the universe's last law, and somehow, he was still here to know it.
The secondary screening room was empty save for a woman in the charcoal-grey uniform of the Temporal Phenomena Institute. Her dark eyes fixed on Callin with an intensity that made him want to check if his skin was glowing. Dr. Mabea Santi, according to her nameplate, Head of Anomaly Detection.
"You've caused quite a disturbance, Mr. Reeh," she said, rubbing her temples. "Though I can't seem to find it."
"I don't understand."
"No, you wouldn't." She gestured to a chair. "Please, sit. Tell me about Andromeda."
The memories came in crystal clear fragments: The colony's vast arcology domes spanning Andromeda's dusty plains. The mathematical patterns he'd found etched into ancient crystals in the deep mines. The colonial scientists' warnings about temporal disturbances growing stronger near the galaxy's core.
"Four days," he said finally. "That's all it took. There and back."
Dr. Santi's expression tightened with pain. "Impossible. The Law—"
"I know the Law. Intergalactic travel is one-way. Time dilation ensures no one returns to their own era. Except..." He spread his hands. "Here I am."
"Here you are," she agreed. "When you should be either millions of years in the future, or..." She trailed off, and a flicker of movement caught his attention. In the corner of the room stood a figure that hadn't been there a moment before – human-shaped, but wrong in ways his mind couldn't quite process. Its edges seemed to blur into mathematical equations that hurt his eyes to look at.
It raised a hand in what might have been greeting. Symbols flowed from its fingers, forming patterns that somehow resolved into meaning in Callin's mind: The foundation fractures. The Law weakens. You are both symptom and catalyst.
When he blinked, the figure was gone. Dr. Santi was staring at the same corner, her face pale with recognition.
"You saw it too?" he asked.
She nodded slowly. "We call them Observers. They appear when the Law is about to be enforced." Her hand moved to her temple again, massaging away what looked like a familiar pain. "But you're still here. Still human. Still when you shouldn't be."
Outside the window, transit pods continued their endless dance along the space elevator's tether, carrying humanity's children to and from the stars. Callin watched them, remembering the crystalline equations he'd found in Andromeda's mines. They'd seemed to pulse with their own light, like the beating heart of some vast cosmic machine.
"What happens now?" he asked.
"Now?" Dr. Santi managed a grim smile. "Now we figure out why the universe forgot to make you disappear."