The original negative was examined and showed no obvious evidence that another photograph had been deliberately combined with it. That ruled out the simple explanation that someone had later edited a person into the image. The most likely explanation was far less mysterious: an unnoticed passerby had been caught at exactly the right moment, with shadows, distance, and the limitations of the old camera making the person appear unusually pale and distorted.
So the unsettling detail is the human-like figure seemingly standing behind the couple. The photograph itself was genuine, but an accidental combination of perspective, lighting, and timing transformed an ordinary background stranger into something that looked almost impossible. Once you notice the figure, it becomes the first thing your eyes return to.
