'The formula was perfect.' That phrase (wrong!) kept running through Sherlock's head as Lestrade recklessly drove him back to 221B Baker Street. Lestrade wouldn't look at him, focusing on the road ahead, steering wheel clenched in a white-knuckled grip.
Sherlock found himself trembling uncontrollably. He clenched his hands into fists trying to quell the shaking. 'How could this happen?!' He forced his mind away from his treacherous body ('transport, just transport') to determine how he'd ended up here…
Since Uni, Sherlock had been suppressing not only his Heats (unbearable, awful, uncontrollable) but his very Omega biology. The concoction, he had created through very careful trial and error using only himself as the test subject. Once he perfected his solution, he took to injecting himself weekly to ensure he would pass as a Beta and not be subjected to the mindless Heats he's suffered through since he was 16. This method had worked wonderfully for years; most immediately accepted him as a Beta. A few people initially assumed he was an Alpha due to his aggressive, some would say obnoxious, behavior, until they noticed his scent, or more specifically, the lack thereof. This made it so he could focus solely on the Work, that which sustained him.
When Mycroft and Sherlock realized Moriarty's end game, Sherlock took it upon himself to tinker with his suppressant. If he was off running across the globe taking down Moriarty's web, he couldn't very well be giving himself weekly injections. The need to be constantly in motion, the possibility of fleeing without his belongings, made it so he couldn't be possibly be succumbing to a Heat in a strange location most likely surrounded by enemies. He had changed the formula to one that was long-term, with the possible side effect being that it might be permanent.
Whatever the case, it had obviously failed him. Sherlock thought perhaps he'd merely been coming down with a touch of the flu that John told him was going around, keeping the doctor busy at his surgery and unable to join the detective at the latest crime scene. Sherlock ignored the signs his body presented him with until he was greeted by Lestrade upon arrival. When Sherlock approached the older man, he felt his insides clench uncomfortably and a sudden, strange warmth coiled in his gut. He shook it off and moved to walk past the DI when Lestrade's scent enveloped him like a warm breeze and his knees almost buckled. His scent was literally mouthwatering. He smelled like leather and musk and, above all, like he was meant to belong to Sherlock. Lestrade's eyes widened as he reached out to the steady the younger man but once he touched the detective, his nostrils flared and his gaze darkened. Sherlock leaned into the older man, and unconsciously tilted his neck, presenting it in typical Omega behavior, responding to a compatible Alpha before he knew what he was doing.
Suddenly, Sherlock realized what he was feeling. It had been years since he'd had to deal with the signs of an approaching Heat but that was obviously what was happening now. His body was reacting to Lestrade's presence. He'd always been attracted to the older man but had subsumed such desires to focus on his work. He'd created his suppressant to control his biology and no matter how handsome and charming Lestrade was, Sherlock had done his best to keep him at arm's length once he realized the depths of his desire. Over the years he'd noticed Lestrade's fleeting glances and steadfastly ignored them.
But now, Sherlock wanted nothing more than to curl up next to the older man. To wrap himself around the DI and feel Lestrade's warm skin slide against his own. He wanted so badly to be marked and taken by the older man andbe filled in a way he had never been before. Oh of course there were some unsatisfactory adolescent experimentations with Omega toysbefore he determined to not let his biology dictate the course of his life. He knew it would be different with Lestrade. That Lestrade would take care of him, would know what to do, how to make Sherlock's body sing.
The part of Sherlock's mind that was still rational was dismayed by the nature of his thoughts as well as the realization his entrance had moistened immediately while his cock began to stiffen. The DI grabbed Sherlock's arm and pulled him away from the crime scene. "Sherlock, what the bloody hell is going on?" he hissed. "You smell like… But you can't…How is that…? What is…? Fucking hell…!"
If Sherlock had been his normal self, he would have mocked Lestrade's sudden inability to form complete sentences. As it was, all he knew was that he wanted to suck the DI's tongue into his mouth and drown in the sensation of the other man's scent, taste, and touch. Lubrication began leaking down his upper thighs.
Lestrade inhaled sharply, shook his head once, and said brusquely, "Come with me, explain on the way. I'm taking you back to your flat."
Sherlock practically melted into the older man. "Lestrade," he said thickly, "this can't be happening. My suppressant can't fail. I perfected the formula."
The DI snorted, "Obviously not", while bodily forcing Sherlock into his cruiser. Sherlock curled up into a ball and did his best to ignore his body's demands, immediately retreating into his mind.
Lestrade was having trouble concentrating on the road. 'Sherlock is an Omega!' kept running though his mind on an endless loop. He smelled amazing, like spice and smoke and home. It was all Greg could do to keep driving to Baker Street and not pull over and launch himself at Sherlock. He'd always fancied Sherlock - 'just look at the man!' - and cared for him deeply ever since he'd found Sherlock during a routine drugs bust. Something about the rail thin young man with the blazing, intelligent eyes struck a chord deep in Greg. He took it upon himself to help Sherlock get clean, managed to get him access to cases at the Yard and never turned his back on him, even when he relapsed. Lestrade was so proud of the five years Sherlock had been clean. Well, seven years now. Lestrade shook his head, Sherlock "died" and was gone for two years. Two horrible years. He thought he failed the younger man. That arresting him was the final straw that drove Sherlock to kill himself. Those two years felt like an eternity.
Lestrade had been beyond thrilled when Sherlock was 'resurrected' like Lazarus and came back into his life. It seemed things were like they were before Moriarty, before Sherlock's fall. They fell back into the easy companionship and working relationship they had enjoyed for years, working alongside each other comfortably. At times John was there as well, when the doctor wasn't busy with his new wife, enjoying a simple Beta life together. He always liked the former military man and the steadying influence John has on Sherlock.
Lestrade was attracted to everything about Sherlock but he knew deep down that Sherlock, as a Beta, could never take his Alpha knot. Never mind that Sherlock seemed to shun most personal relationships and had never had a romantic entanglement as far as the DI knew. Lestrade valued Sherlock too much in too many ways to risk him shunning Greg if his feelings were known. So he let the status be quo. He worked with Sherlock and welcomed him back with open arms when he returned from the dead.
'Black is white, up is down', Lestrade thought, a tad hysterically, as Sherlock's amazing scent filled his nose. The detective wasn't a Beta, had never been a Beta. How was such a thing even possible? He smelled so clearly like Omega now but before he'd always presented as Beta. Sherlock always smelled lovely to Greg but never like this. Sherlock hadn't been very clear when Lestrade dragged him away from the crime scene smelling like an Omega about to go into Heat. Something about his suppressant failing, which the consulting detective kept repeating was impossible. Lestrade hustled him into his car, opening the windows despite the winter chill and headed to Baker Street at a breakneck pace.
He chanced a peek at his passenger seat. Sherlock was huddled against the window, visibly trembling and throwing off waves upon waves of delicious pheromones that screamed at Lestrade's primal instincts. It was his concern for his friend that managed to pierce the haze of lust and allowed Greg to focus on the road and delivering the detective to his home unharmed. 'I will control myself', he thought fiercely. He would take Sherlock home and leave him untouched. Lestrade forced his mind to ignore his baser urges. His instincts urged him to take the younger man, to mark him as his, to fill him with his Alpha cock and knot him as he screamed Greg's name. His cock strained against his trousers. He shifted uncomfortably and Sherlock moaned softly.
It was a miracle they made it to Baker Street in one piece. What happened next was either destiny or a cosmic joke.