As they're getting ready to go to dinner, Sherlock smiles down at John and murmurs. "You're looking positively incandescent tonight."

John beams. Sherlock's sparse with his compliments, but when he gives them, they're genuinely deep and touching.

"And you, Sherlock, are absolutely luminescent."

Sherlock's face falters for a second before he smiles. John notices, and pauses.

"Did… Did I say something wrong?"

"Is that really how you see me, John? Bright, but cold? Radiating plenty of light but little in the way of heat?"

Confused, John raises an eyebrow. Sherlock takes this as an invitation to launch into a painfully detailed explanation of the difference between hot body radiation and cold body radiation. John's eyes glass over just before Sherlock wraps up.

"Thank you for explaining all that, Sherlock. I never meant to upset you. I honestly didn't know the difference. You may be a bit obtuse sometimes, and you're not always emotionally forthcoming, but you're not cold. Bright, yes. Impossibly so. But definitely not cold."

Sherlock smiles, somewhat mollified. If anyone else had called him cold, inadvertently or not, he'd have proudly agreed with them. However, coming from John, he has to confess to himself that it hurts. Sherlock finds himself musing that despite all their years together, flattery is still exciting, and he's glad John still finds him bright.