Sherlock is on stair eight of seventeen when he realises that something doesn't smell quite right. It's weak enough that he chalks it up to the ongoing experiment in the kitchen sink and continues on his way.

He's on stair twelve when he hears something not quite right. This leads him to revisit the not-quite-right smell and to reconsider his assessment thereof.

The smell: organic but of animal rather than plant origin, musky, thick in a strange way that tickles at the back of the soft palate.

The sound: a grunt, low register, rough. Structured, strangely enough.

More data needed.

Sherlock ascends the remaining five steps silently. The scent is stronger here, as are the sounds coming from the flat. He puts his ear to the door, wondering if perhaps he's come home to John fornicating with someone in their parlour. He hates it when John does that. The scents are overwhelming.

The grunt goes again, followed by a complex series of grumbles, croaks, clacks, and stops.

Emphatically not John, coital or otherwise. He is English through and through, and unless he was exposed to several different African tribal languages as a child, he should not be capable of producing such sounds.

In fact, now that Sherlock considers it, he's not sure he's capable of making such sounds, and he's functionally conversational in a few African languages (Swahili, !Xuun, and Fulani).

Sherlock's extrapolations are shattered as definitely-John's-voice produces a passable imitation of the strange, guttural sounds. It's not the same patterns, though—is he conversing with someone through such... noise?

Too curious to remain outside the door any longer, Sherlock straightens up, squares his shoulders, and opens the door.

John is seated in his armchair, but the coffee table has been cleared off, set on its edge, and leaned against the wall to make space for...

... well. Sherlock's not entirely sure what it's made room for.

On second thought, he has absolutely no idea what it's made room for.

The thing takes up as much space as a small pony, and looks like it might mass a little over one hundred kilograms. It has an ovoid body roughly the size of a large human torso, roundish in front and slightly tapered in the rear. A short trunk that reminds Sherlock of a tapir's snout dangles from the front of the body; stalk eyes much like those on crabs or lobsters perch atop the head(?) section. Smaller, eyeless tendrils that appear to be sensory organs of some sort surround the bases of the eye stalks. It appears to be endoskeletal, as it is covered in a muted, lichen-blue skin that fades to white on its belly. It has four legs that sprout from its sides, like a lizard's; however, unlike a lizard's legs, the creature's limbs are long and constructed in such a way that its knees (one and one third of a metre above floor level) are considerably higher than the level of its back (three quarters of a metre above floor level). The limbs are long, powerfully muscled, and seem similar to human legs, if human legs were rather longer and skinnier than typical, but end in feet with four long, strong toes arranged radially around a central pad. The feet look dexterous and well-suited to gripping, manipulating, and climbing.

Incongruously, it appears to be wearing a Doctor Who backpack emblazoned with colourful Daleks.

Sherlock isn't sure what sort of noise it is that leaves his mouth, but it startles John out of his shocked staring and the armchair. "You were supposed to be in Monaco! You weren't supposed to be home!" he squawks, slamming the door shut behind Sherlock and throwing the lock. "What are you doing here!?"

"Case was boring," Sherlock says, on autopilot. Distantly, he thinks that perhaps his brain is experiencing something similar to a kernel panic and wonders if he remembered an auto-restart protocol in case of such an eventuality. He goes looking for it but gets distracted when he wonders why there is a strange, fleshy, grey-blue daddy long legs in their sitting room.

"Ambassador (here John fluently makes a series of noises: "clickgroan upward grunt rattling-cluck") is not an arachnid," John scolds gently. "Shi's stopping in on hir way to the Draco Tavern in Siberia; shi'd heard I was home from Afghanistan and wanted to catch up." He chivvies Sherlock around Ambassador Clickgroan-upwardgrunt-rattling-cluck (who obligingly lifts one foot out of the way of his shuffling) and sits him down firmly. "Stay here, don't touch, and for God's sake don't take pictures. Had to wipe an entire unit's memories back in Kabul when some smartarse thought he'd send his selfie with a sparked-out Chirp pilot to all his mates. Expensive as fuck to clean up, that was, and I don't want to have to meddle with that brain of yours."

The Ambassador rotates in place (Sherlock dimly notes the way it moves one foot at a time, so there are always three feet on the floor) to face Sherlock. Its expression (if it has any) is inscrutable, but it's obviously giving him a very thorough looking-over.

The Ambassador noises, and the sensory tendrils about its eyes wiggle. Sherlock jumps. John laughs. He noises back, waggling his fingers in a rough approximation of the motions of the Ambassador's sensory tendrils. The Ambassador produces another stream of noise and wiggles, and John curls all of his fingers once. This seems to have some meaning, because the Ambassador turns back to John. They resume their cacophonous, wriggly conversation with all the chummy camaraderie of longtime friends.

Sherlock lowers himself to the couch, turns so his back faces John and the Ambassador, and hugs his knees to his chest. Whatever he decided to experiment with, it must have been a real stonker of a hallucinogen—he's never had delusions of aliens before. He can't even remember taking anything. God, how bored had he been?

He glances over his shoulder when there's a lull in the noise. John is typing blisteringly fast on a transparent screen that hovers in the air. Ambassador Clickgroan-upwardgrunt-rattling-cluck is looking at Sherlock again.

Sherlock turns away and pulls one of the sofa cushions over his head.

Whatever it was he took, he resolves never to do it again.

Ever.


.


Oh God.

I have no idea how this happened.

It was half past midnight and I was going to go to bed. Then suddenly it was four AM and this was on my computer.

The Ambassador is a Ch't'nduar'l, a hermaphroditic, semi-arboreal species of extraterrestrial I concocted in a fit of boredom about six years ago.

The Draco Tavern, Chirpsithra (Chirps), and sparkers are the delightful creations of the inestimable Larry Niven. If you're interested in really alien aliens, short stories, and bars that cater to extraterrestrials in Siberia, I highly recommend you give "The Draco Tavern" a shot.