This takes place around 2003, very near the beginning of Sherlock's career as a consultant and will be in a couple parts. The backstory I'm assuming is that Lestrade forced Sherlock to go clean before letting him work with the Yard. It's meant to explore the mentorship and frustrated admiration of Lestrade, as well as the trust Sherlock has for him. Disclaimer: I don't own Sherlock or the show, obviously…
Sherlock sighed and tried to stand up. His bruised ribs protested and his head swam at any attempt at movement. So nope, bad idea, staying on the ground for now.
He reached for his phone and was relieved to find it undamaged. With shaking fingers, he composed a text to DI Lestrade. He still wasn't sure what to think about the detective inspector, but Lestrade seemed trustworthy. He was, after all, the one who let Sherlock in on the case in the first place, albeit accidentally.
Tracked suspect to warehouse on the corner of 3rd and St. James. He is restrained. Please come as soon as possible. –SH
That didn't sound like begging, he thought. It was also mostly true, except for the restrained part. The suspect was actually lying unconscious on the warehouse floor currently. Restraint could be arranged, though, thought Sherlock as he slowly dragged himself to his feet, ignoring the temporary loss of vision and immense pain in his side. His stomach roiled, and he was glad he'd barely eaten anything all day. Or the day before. Diagnosis: mild to moderate concussion, 3 ribs bruised, none broken.
The large, mostly abandoned warehouse came back into focus as Sherlock leaned against a pillar, breathing sharply through clenched teeth. The suspect would regain consciousness in a matter of minutes. To start off, Sherlock tied his scarf tightly around the man's wrists behind his back, but it wouldn't last. Neither would Sherlock's strength, as upon a second attempt to stand and procure the roll of duct tape he'd noticed in the random debris on the warehouse's shelves, he collapsed to his knees and endured several rounds of dry heaving.
When his stomach had settled a bit, Sherlock slowly walked to the shelf where the dusty tape sat, bracing himself against the wall with a bloody, trembling hand the whole way. It took all of his remaining strength to drag the unconscious man across the floor to the nearest pillar. Once the suspect was thoroughly secured to the pillar with his hands behind his back, Sherlock didn't even have the energy left to tear off the tape. His eyes were heavy and every time he moved it felt like his brain was ripping apart.
When the police entered the warehouse, Lestrade at the head with his gun drawn, Sherlock was slumped against a wall, head in his hands. Lestrade commanded a few of the officers to check on the suspect and handcuff him, and turned to his consulting detective with a worried look.
"Sherlock! You alright?"
Sherlock lifted his head slightly. "Took you long enough," he drawled, before letting his head fall back and groaning.
Lestrade rushed forwards and crouched next to him. "Sherlock? Talk to me, where are you hurt?" he asked.
Sherlock didn't bother to lift his head, and when he spoke his words were slurred and pained. "He… hit me with the… the gun in the corner," he gestured vaguely and Lestrade shouted for someone to get it, "Got concussion… couple bruised ribs… nothing major. Just need… couple minutes."
Lestrade stood to observe the handcuffing of the suspect, who was gradually coming to. Sherlock looked up as the suspect grumbled, "Whassa? Tha' freak— Knocked me out!"
"Self-defense!" cried Sherlock from the floor, breath strained. Lestrade turned back to him and leaned over to inspect the head wound. He pushed the younger man's curly fringe out of the way, trying to be gentle. Sherlock winced.
Lestrade stood and pulled out his phone, "I'm calling an ambulance."
Sherlock groaned. "No… no hospital."
Sherlock tried to push himself off the ground, but Lestrade held him down with a firm hand on his shoulder. Sherlock reached up to clutch at his wrist desperately. "No. Hospital." Lestrade crouched down, trying to meet Sherlock's unfocused gaze.
"Come on, kid. You'll be okay."
"I know," said Sherlock, "I'll… call a… a cab."
Lestrade sighed. "Can you even stand up?"
Sherlock tried to hoist himself up using the wall. His legs were shaking and there was a fuzzy blankness taking over his vision, but he made it to his feet. Blinking furiously, he swayed a bit, before Lestrade's hand on his shoulder steadied him. "Okay, I'm taking you to the emergency room right now."
Sherlock shrugged off Lestrade's hand and backed up to lean on the wall. "You have… to arrest—"
"They're taking him away, they don't need me." Sherlock looked up and took in the rest of the scene. It was true, Sergeant Donovan was nodding her agreement as Lestrade motioned her to go on without him.
Sherlock mumbled, "I don't… need you either."
Lestrade ignored the consultant's feeble attempts to swat him away and pulled the younger man's arm over his shoulder, grabbing him by the waist. Sherlock cried out in pain, and Lestrade loosened his grip slightly. "Sorry, Sherlock. I'm taking you to the hospital."
In a sudden burst of adrenaline, Sherlock attempted to push away the older man, making it a few steps away before his vision clouded over completely and his head spun. He felt hands grip his shoulders just before his knees collide with the ground and suddenly Lestrade's voice was very close. "Work with me here, I'm trying to help."
Sherlock took a deep, wheezy breath. There was panic in his voice, uncharacteristic of his usual deep tone. "The hospital— they'll give me… for the pain… I can't…"
It dawned on Lestrade what Sherlock meant. The man had only been fully clean for a couple of weeks, and one dose of morphine or a few Oxycontin could set him back months. "Hey," Lestrade started, cupping the back of Sherlock's drooping head, "I'll take care of that, okay? I'll make sure they don't give you anything, don't worry. You just have to get that looked at."
Sherlock's vision cleared enough for him to make eye contact with the inspector, who was examining him with genuine concern. He started to stand, and Lestrade helped pull him to his feet. "Okay," he said thickly, leaning heavily on the older man as they made their way out to the car.