Another Kind Of Memory (слэш)

'What happened to your back?'
Arthur's voice sounded tense, stiff and uncertain. The brush of warm fingers against the three, pale lines across his shoulder-blade made Merlin jolt in alarm. He whirled around, the tunic still clutched in his hands as he blinked stupidly, his words caught somewhere in his throat.
Not that it mattered. Arthur was too busy staring at the starburst scar the size of a grown man's hand that lay right in the centre of his front, over his heart. A frown of confusion melted beneath a mask of horror, and Merlin swallowed hard as all the colour fled Arthur's face.
'What happened to your chest?!'
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(Prompt: Incendiary - for Seadeepy)