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John had got so used to seeing Sherlock leap up ten foot jumps and over wide chasms between buildings, that he was fairly sure he was part cat. The difficulty always came when Sherlock expected him to follow, which was worryingly often for a man rapidly approaching forty.
Today, like many other days in London, it had been raining. Today Sherlock took them through back alleys in Tower Hamlets, up a fire escape and across a corrugated iron roof. And so, today John’s foot slipped from under him, and when he crashed to his knees the whole flimsy structure gave way and he and the sheet of metal tumbled hard to the ground.
When the stars before his eyes cleared Sherlock was kneeling over him, calling his name. He blinked hard and shook his head.
“I’m fine,” he replied. “Go on, you’ll lose him.”
Sherlock hesitated. “Are you sure?”
“Yes. Go!”
He rose to his feet and began to turn, only to freeze.
“John...”
“Go on!”
“John, is your leg supposed to be at that angle?”
John looked down his body. His lower right leg was lying angled away from his body, looking nothing but unnatural.
“No,” he said, “it’s not.”
He felt the blood drain from his head and heard Sherlock call his name urgently as the world turned black.