Here's your text with some proofreading, expanded detail, and a touch of fantasy, while maintaining your original storyline:
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"We should return to the castle. The hour of luncheon is approaching," he breathlessly uttered, glancing down at his wristwatch, its face glinting in the dappled sunlight. He noticed her nod in agreement, and together they made their way back to where Sylve was tied, crouched on the grassy ground, her eyes closed as if lost in a dream.
...
The couple rode back to the castle, the sound of hooves echoing softly against the cobblestones, and indeed met the time for lunch. The dining hall was unusually quiet, a heavy silence hanging in the air, as if the castle itself held its breath. No one spoke much, and the atmosphere felt laden with unspoken thoughts and lingering tension. That was how luncheon ended for the family, a meal marked by shadows rather than warmth.
