Trial by Fire
There was a crash from downstairs, clearly audible in 221B. Sherlock's eyes flashed open to catch John's gaze. They paused for a moment before John moved from his chair to the door and stuck his head through into the hall, Sherlock shadowed him instantly.
"Everything ok, Mrs. Hudson?" John shouted down. There was no response. John shrugged and turned to look at Sherlock, who quirked a brow in question. Suddenly they heard Mrs. Hudson come out from 221A and give a gasp.
"You've brought the smoke alarm down!" She shouted up the stairs in response, she sounded irritated.
John let out a sigh of relief and released his grip on the gun that was automatically in his hand. "Erm... Sorry?" He called down to her. He turned to look at Sherlock who had straightened, his face impassive. He bustled past John and down the stairs. John took the time to return the gun to where it had been, wedged between his armchair's cushion and the arm. Then he followed in the detectives wake.
He found Sherlock and Mrs. Hudson standing around the smoke alarm which was on the floor in the buildings main hall. It had split into a few pieces and the battery had skittered away somewhere.
"How did we cause that?" John asked confused, looking from it to its mounting still screwed to the ceiling.
"Vibrations!" Mrs. Hudson said plainly. She folded her arms and raised an eyebrow, "this will be put on top of your rent boys!" She didn't seem in a cheery mood today at all John thought glumly.
"Er, right. Sorry again.." He said slowly. Sherlock quickly and deftly gathered up the parts of the smoke alarm and planted a quick peck on Mrs. Hudson's cheek.
"I'll fix it." He flashed her a smile and rushed past John back upstairs. John turned to look at their landlady and her features had softened.
"Away with you! Before he causes more trouble with it than its worth!" She smiled as she disappeared back into 221A. When John got back upstairs Sherlock was already busying himself with the smoke alarm at the kitchen table. John scratched the back of his head absent-mindedly,
"Could vibrations have done it?" He asked slowly, not quite grasping the concept.
"Obviously."
"Obviously.." John echoed almost to himself. Sherlock heaved a sigh.
"Well the clips that secure it to the ceiling were not broken and you have to twist it to remove it, so the logical explanation is that gradually it has shaken itself free due to vibrations. Our flat is directly above and undoubtedly the most busy so it's a sound conclusion." He said quickly.
"Ah, obvious." John said mocking Sherlock's deep voice. Sherlock did not look impressed and continued to study the smoke alarm in hands. John took the seat opposite at the table to watch him. Sherlock clipped into place the small case which held the radiated atoms. John was vaguely surprised Sherlock wasn't dissecting it to reveal the element within. Another part which had come loose was quickly put back in its place. then the plastic cover was snapped back on. He flipped it in his hand. Sherlock then produced a battery and put it in its slot, there was a brief blip then nothing. His long fingers tapped the test button but no sound emitted. He pulled the battery out again and tried to find the problem. Both the terminals were there and the battery was being put in the right way round.. He tried again to no avail. A frown growing on his brow. He looked closer,
"The terminal isn't touching the battery!" He offered it to John who looked and confirmed that indeed there was a small gap between the positive terminal and the small folded metal strip that was the smoke alarm's corresponding terminal. Sherlock frowned then got up and rifled through one of the kitchen drawers. He produced a fork and took the smoke alarm back and started to pry at the metal terminal on the smoke alarm. After what he believed was sufficient prying, the battery was reinserted but nothing.
"Maybe the battery is flat?" John offered but Sherlock was not to be put off so easily. He continued to pry and poke and reinsert the battery but all that he could manage was a few meagre blips here and there. His attempts had failed. He huffed, absent-mindedly poking a nail file- which had joined the array of "tools" -into the gap between the battery and the stubborn terminal.
BLEEP!
The alarm let out a sudden loud cry which made both Sherlock and John jump, John laughed at his surprise and Sherlock joined in the chuckling.
"So the battery isn't flat, the terminal just still won't reach." Sherlock sounded a bit flummoxed. So John offered to try. He looked at it carefully.
"Well as the battery hits the negative terminal this one also moves back, the metal strip is all one unit" he said thoughtfully.
"Yes I know that." Sherlock snapped, annoyed more at the inanimate object than John. The shorter man started to pry the plastic case back off which Sherlock had reattached. He pushed the metal strips forward and attached the battery. He pressed the button but nothing happened. His face also fell into a frown then, he had believed he had cracked it. He put it down then and got up to make tea instead. Sherlock re-examined it more closely this time and noticed that the circuit board was out of place and that was throwing the terminals out.
"Aha! John I've got it!" He said pleased, as he popped the circuit back into place then tested it. The alarm rang out clear as a bell. Sherlock grinned happily and reassembled the whole thing.
"Only thing left is to reattach it to the ceiling!" and with that he was gone. Five minutes later he returned to the flat still looking pleased with himself. John watched him with an amused look.
"What?" Sherlock asked when he spotted him.
"Oh nothing!" John said, taking a sip of his tea "we just need to find you a case, and quick. You're becoming domestic!" John grinned and dodged the cushion which came flying at his head.