The air's definitely getting thin now. Sherlock can feel himself slowly growing sluggish. His breaths are becoming shallower, his body working on instinct to preserve what he can. He can hear John breathing, the sound of the cab making it's way to the yard and takes comfort in it.
"John." Sherlock rasps. His voice is quiet, he's most likely dehydrated, John thinks.
"Sherlock. Are you alright?"
The man snorts. "I've been better."
"We'll be there soon. We'll get you out." John can hear Sherlock take a shaky breath.
"Good, good." Sherlock's voice is tight, brittle, reminiscent of the time Sherlock had broached the subject of John's nightmares, when John had appeared in the living room at 3am to curl up in his armchair. John had answered in single syllables, his face blank. Sherlock had dropped the subject, realising that John needed the relative normality of their interactions rather than an ear. Sherlock had picked up his violin and lost himself in the familiar movements until John had nodded off once more. "The air's getting a bit thin, I think. I'm not dizzy, yet, so that's something."
"Good. That's good," John isn't sure what else to say. "Two and a half hours. That's more than enough time to find you." No it isn't, John thinks.
"Two hours and twenty minutes now," Sherlock corrects.
"I'm almost to the Yard-" John stops talking when he hears rustling around on the other end. "Sherlock? What are you doing?"
"Dammit!" He hears Sherlock exclaim, but his voice sounds far away. "John! The phone is about to-"
John's phone suddenly beeps to indicate the call has ended.
A/N Sorry for the short update, but I wanted you guys to know that I haven't abandoned this story and longer, action chapters are coming!