John Watson's smile was uncontrollable. To any observer, his features would have seemed at war with themselves, at some times tamping down on the grin, at others releasing it to its full, slightly manic effect. "Sherlock," he called out cheerfully, "I'm home!"
"Glad it's not a burglar, then," Sherlock murmured dryly, not looking up from his newspaper. "Did you get the parchment paper?"
"Yes," John said as patiently as he could manage, laying the shopping bag's bizarre contents on the kitchen table. "And the newts, and the rock hammer."
"And..." He pulled out the bag's final item before concealing it behind his back, "I brought you a surprise."
"Come, John, we both know that's impossible," Sherlock assured him coolly. His leafing through the newspaper soon grew quicker and more violent. "Arson, accident, kidnapping, faked his death, dull, dull, dull!" Finally, he folded it in half and thrust it in the direction of the fireplace.
"But as London's criminals have apparently taken the week off, and I seem to have nothing better to do, let's have it." He tapped his fingertips together expectantly.
"It's your favorite game," John announced with ill-concealed glee. With a flourish, he produced an oblong box of medium size, wrapped in shining blue paper with silver ribbon and a matching bow, and placed it ceremonially on the table beside Sherlock. "Ta-da!"
Sherlock shifted his gaze between John and the newly displayed object suspiciously. "You swore we'd never play again. Not after the parakeet."
"Oh, I know, I know, I know," John said impatiently, pushing the box in Sherlock's direction. "I changed my mind, all right? I think you'll find this one a real challenge."
He began to reach for the box, then paused to ask, "And it's not another parakeet?"
John shook his head, his smile now bordering on the verge of unhinged. "No, definitely not another parakeet."
"Or anything else I'm liable to injure with a sound shaking and thus incur the continued wrath of Mrs. Hudson?"
"Oh, it's too good," John muttered to himself, before pronouncing, "No, shake away, Sherlock, you won't hurt it."
With the formalities dispensed with, Sherlock turned his full attention to the box. Eyes closed, he traced long fingers across each side, muttering measurements. He lifted it to his ear and shook it one, two, three times before returning it to the table. By this point, his stream of deductions had become loud enough for John to make out.
"Initial description means it can't be alive or fragile - almost certainly not perishable either, not after the yogurt incident. Box is peculiarly shaped, but sure to be a double blind. Quality wrapping material, could be another misdirect, yet the execution indicates significant care and skill, almost as if performed by a...a professional..."
Sherlock stopped mid-sentence and stared, wide-eyed, at John.
John rocked back and forth on his heels as he announced in a sing-song voice, "You can try all you like, but you're never going to guess it."
"Yes, well." Sherlock's voice had grown uncharacteristically quiet. "I suppose we'll see." He scrawled a single word on the nearest scrap of paper and pushed it, face down, in John's direction.
"I know it's not the done thing, but I'm going to open this one," John said. He made quick work of the oblong box to reveal a smaller, rectangular one inside it. His fingers clenched it tightly as he got carefully to one knee and began.
"Now, Sherlock," John cleared his throat, "I know this is going to require some mental adjustments on your part, but hear me out. You and I -"
"Look at the paper, John," Sherlock said. His expression remained inscrutable.
"Would you just -" John's clenched his fists, took a breath, and counted to three. "Let me finish? It kinda affects the rest of our lives."
Sherlock simply slid the paper forward. "Please, John."
Letting out an exasperated sigh, John unfolded the paper. His voice caught as he read aloud the single word printed on it: "Yes."
Sherlock looked at him intently for a few moments before allowing a small smile to creep onto his face. "I guess that means I win." He extended a hand in John's direction.
John let out a chain of sputtering laughs, at the end of which he levered himself upright via his partner's offered hand. He then threw his arms around Sherlock's neck, murmured fondly, "Oh, that's what you think," and kissed him hard.
The box lay on the table beside them, both question and answer contained within.