Disclaimer: I own neither Sherlock nor Torchwood. All rights belong to their respective owners.
When Sherlock arrived with John at the crime scene, he was surprised (and also quite a bit angry) to see Lestrade in the middle of a conversation with a handsomely-featured (probably) man in a WWII-style greatcoat. Standing beside the two was a dark-haired woman, who wore a bemused expression on her face.
"I've never even heard of Torchwood!" Lestrade told the man in an exasperated tone. Sherlock noticed the large vein sticking out of the detective inspector's neck.
The man had just opened his mouth to reply when Sherlock decided to interrupt the argument. "I thought we had an agreement?" Sherlock said to the man, who quickly turned around at the sound of the consulting detective's voice.
"Sherlock?" he replied. "Oh great..." he sighed. After a beat, "Roshambo?" He stuck his fist out then, ready to do what needed to be done.
"I don't see why that's necessary," Sherlock scoffed. "Are you sure this falls under your area of expertise?"
"Not yet," admitted the man. "But I definitely have a strong suspicion."
"And after I check in with the higher-ups," Lestrade interjected, already whipping out his mobile, "I'll be sure that you won't ever know the answer." He turned away then, absolutely missing the interloper's eye roll.
"I'm sorry," John said, filled with curiosity. "Do you two know each other?"
"Quite," was all Sherlock answered.
The man, however, flashed a smile and extended his hand, "Captain Jack Harkness," he said. "And who are you?"
John blushed a bit and introduced himself. "Dr. John Watson. Pleased to meet you."
"Likewise," Jack grinned.
"Oh, stop it!" Sherlock spoke, clearly vexed. "This is a crime scene, not an orgy. Put it away for once."
Jack held up both hands as a sign of surrender. "Alright, alright."
The woman beside Jack who had been quiet since Sherlock and John's arrival, began to chuckle. Sherlock turned to her then, "Hello, Gwen Cooper. I see you're still alive; quite a feat considering with whom you work."
"Never underestimate a Welsh woman," she replied. "But I'm not playing referee between you two children, so you better decide who's staying and who's leaving. I've got better things to do with my time."
"I have the distinct impression that I'm missing something," said John.
"So the status is still quo," Sherlock huffed in annoyance.
Intentionally ignoring Sherlock, John turned to Gwen and asked, "Do you ever have to put up with this sort of thing?"
"Not to your degree, no," Gwen told him. "But I do constantly feel like I'm stumbling around in the dark when I'm around mine." She said the last word with a nod to the head toward Jack. "So, gentlemen," she said, addressing both parties. "Have we made up our minds yet?
Jack let out a deep breath. "I'm willing to put differences aside," he said, "just as long as he promises not to kill me this time."
"Oh, you're fine," Sherlock sighed. "Anyway, it helped us catch the fellow."
"Still," said Jack. "I'm also capable of enduring a root canal- doesn't mean I'm willing to have one just because I can."
Sherlock paused for a moment, considering. "I suppose combining both our assets could turn out to be beneficial..."
"I better phone Rhys then," sighed Gwen. "Tell him he'll be looking after Anwen alone for a few days."
"God help him," Jack smiled in a friendly manner.
"Rhys is a good father!" she protested, though a slight smirk could also be detected on her lips.
It was then that Lestrade returned, shoulders hunched and a crease between is brow. "I don't know who you are, Captain Harkness," he said. "But you best try to avoid my cases from now on. Sally!" he called out. Sergeant Donovan quickly appeared by his side, taking a brief moment to fit in her obligatory sneer at the Freak, and then, noticing Jack, looked him up and down with an approving stare, too obvious for Sherlock's liking.
"Yes, Sir?" she answered.
"Tell everyone to pack up," he ordered. "We're off the case."
"Sir?" she asked quizzically.
"You heard me, Sally," he said.
Silently, she gave him a wary glance before turning to carry out his orders.
"You're better off without this case, anyway," Sherlock said, not exactly trying to be comforting. "There are some things you just don't want to know."
"And you?" Lestrade inquired.
"I already know them," answered Sherlock.
"Of course you do," sighed Lestrade. Without a goodbye, he turned and left.
"Well," said Jack, once the four of them were relatively alone again. "Shall we get started?"
"I think I deserve some explanation first," said John. "Don't you think?"
Sherlock, Jack, and Gwen exchanged uneasy glances.
"Roshambo?" Jack suggested.