The train rattled along the tracks, a rhythmic clatter cutting through the silence of the midnight commute. The few remaining passengers—scattered across the dimly lit car—sat hunched in their own worlds, faces buried in books, phones, or the comforting lull of exhaustion. Detective Elias Mercer wasn’t interested in any of them. His eyes were fixed on the worn leather briefcase resting on the seat across from him. It belonged to the man who had just vanished. Moments ago, the train had pulled into the Washington Street station, and the usual shuffle of departing commuters had ensued. Mercer had barely glanced up—until he noticed something off. The tall man in the gray coat, the one who had been sitting across from him for the past four stops, had risen to leave. But he never reached the door. One blink. One brief glance away. And the man was gone. No movement, no footsteps, no sign of departure—just an empty space and a single briefcase left behind. Mercer leaned forward, studying it under the flickering fluorescent light. The briefcase was old but well-kept, the kind professionals carried. No tags, no initials. Just a single brass clasp gleaming under the glow. He reached for it. The moment his fingers brushed the leather, the train groaned, the fluorescent lights flickered wildly, and the entire world seemed to tilt. A whisper—soft, urgent—ghosted past his ear. “Don’t open it.” Mercer’s breath caught. He whipped his head around, searching the near-empty car. But the passengers—still absorbed in their own late-night distractions—remained oblivious. He was alone. Except for the briefcase. And the man who had disappeared.