When the rattling at his doorknob began, John called out, "That's locked for a reason."

"I'm fully aware of that," Sherlock retorted, continuing to pick the lock.

"The reason," John was now using a tone of voice indicating that his patience was being sorely tried, "is that I don't want you in here at the moment."

"But I'm bored," the detective complained.

"I'm busy right now. Come back later."

Undeterred, Sherlock finished his work, and turned the door handle, starting to swing it open. Only to find himself staring down the barrel of a handgun.

John stood right in the crack of the door, pointing the gun resolutely between his friend's eyes. "Get out, Sherlock."

Though understandably alarmed by this sudden turn of events, the detective scoffed, "You and I both know that you would never really shoot me. Now stop being so childish-"

"OUT."

The doctor's finger tightened on the trigger, causing Sherlock's heart to involuntarily speed up. He stared down at John in hurt betrayal. What could he possibly be guarding so valiantly that he was willing to threaten Sherlock to keep him out? They were friends, right? Weren't friends not supposed to keep secrets from each other? Or had his research been wrong? After another second in which their contest of wills lasted, he reluctantly stepped back. Instantly the door was shut and locked again, confirming his suspicions that something was going on.

As he stood there, Sherlock realized that John had been looking almost...afraid as he stood there threatening the detective with the gun. Even though his hand was steady, his face was pale, his eyes were frightened, and Sherlock could swear there had been a sheen of sweat on the doctor's forehead. Something-or someone-was in his room that he didn't want Sherlock to see. And he wanted to know what.