They arrived at the dance studio with minutes to spare before the start of the couples basic tango lesson.

Sherlock stopped and pulled John away from the door and further down the shadowed hall. "We don't have to do this, John."

John frowned at the hand clutching his arm and up at Sherlock. "What are you on about? You wanted to observe the class, so we're taking the class. Or did you solve already it on our way here?" The purse of his lips expressed how very much that would not surprise him.

Sherlock's mouth curled up in a wry grin as he shook his head. "Not impossible, of course, but no. What I'm saying is we don't have to do this. I can go on my own, they always have assistants or other singles at these things to pair up with. I know you don't want-"

"Sherlock, stop," John said firmly. "We've been over this. I told you I don't mind the dancing. What I do mind is us standing out here," he jabbed a finger toward the floor between them, "when we should be in there," he thrust a thumb over his shoulder toward the studio door, "sniffing out a blackmailer and possible murderer, like we've been hired to do. And even if I wanted to back out, which I don't, it's too late for that since the class is starting in minutes!"

John's eyes narrowed as he paused for breath, "And of course you know all that, so tell me the real problem."

Sherlock sighed and let go of John's arm, crossing to the other side of the hall. He regarded John for a moment with his hands steepled against his lips, then spoke. "If this is going to work, we'll need to be convincing as a couple."

John held up his palms in an 'obviously' gesture. "I know that."

Sherlock quirked an eyebrow, "Do you?" He lowered his hands and slid them into the pockets of his coat. He took a lazy step forward, his eyes lowered.

"We've been flatmates for a while and as such, we have become quite accustomed to each other. But that's not enough, not for this. When we walk into that room, John, we're a couple. We must be more than two men comfortable in each other's presence." Another step brought him close enough for the lapels of his coat to brush the doctor's jumper. John went very still.

Sherlock lifted his eyes and the intensity of his gaze struck John like an electric jolt, but he met it with a steady stare of his own.

Sherlock leaned in close, sending tingles down John's spine. He swallowed hard against the sensation, his fists clenching and releasing.

"No, John, that won't do." Sherlock voice rumbles in his ear.

The detective's mouth was a whisper away from the shell of his ear and John could feel the damp heat of his breath. "We are two men that are familiar with their partner's body. We know each other... intimately."

Sherlock lifted a hand and placed just the tips of his fingers against John's chest. "We're lovers, John."

John felt those fingertips searing through the knit of his jumper like five tiny brands and he felt an urge to mirror the gesture, to put the mark of his fingerprints right into Sherlock's very skin. His hands clenched even tighter to keep them at his sides.

Sherlock stepped back and the sudden space pulled at John to close the distance again. Sherlock pressed himself back against the wall, digging his fingers into the grooves between the bricks.

"In there. In that room." Sherlock bit out the words between breaths. "We are lovers in that room, John. Can you do that? Can you pretend?"

Sherlock's voice is harsh, challenging, and John straightens, takes that step forward and tilts his head up to look him dead in the eye, "Ready when you are."

Sherlock's eyes flash and a fierce grin flashes across his mouth. "I've always been ready, John Watson." He winked and moved past John in a way that could only be described as a swagger.

John took a moment to catch his breath before an answering grin lit up his face and he turned to follow his detective inside.