John wondered if he was trying to grow a particular species of Penicillium. Sherlock had just recently been quite sick and had almost caught pneumonia. John finally had to force him into taking antibiotics, which had just been commented by Sherlock with a flippant: "Dull." In a way, though, Sherlock had somehow been intrigued by John's sermon on the importance and the luck of having antibiotics. John wondered why, because Sherlock had a profound knowledge about antibiotics and the biochemistry behind them. Anyway, since then the milk and bread had disappeared curiously enough, although neither John nor Sherlock ate and drank much of them. Instead, the kitchen table was plastered with petri dishes growing colourful mould. They were nice to look at in a way, however, eating at that same table was currently impossible.
As John hadn't expected anything else but Sherlock forgetting about the shopping, he went to Tesco's himself one day when he really needed some hot tea with milk. However, after yet another row with the automatic check-out, John felt a slight anger rumbling in his gut. On his way home he had bumped into another pedestrian who had insulted him very unpleasantly. One of the milk cartons had fallen to the ground and split, the milk splattering John's trousers. In John's perception the other person had almost tackled him deliberately, but when he had finally collected himself to question the man, he had already run off.
So, when John got home, the anger in his gut had become very dominant and he felt like going into a rant against Sherlock, which would help to make him feel better.
He entered the flat, expecting to see Sherlock stretched out on the couch thinking or just pretending to be doing so. Before John had left for the shopping, the Consulting Detective had been on the sofa, barely showing any reaction to John's moaning about the missing milk. "Need to think", had been the only thing he had mumbled more or less to himself. John scanned the living-room, but Sherlock was nowhere to be seen.
"Sherlock? Back from shopping!"
No reply. John sighed and went to the kitchen to store the shopping. He jumped a little when he saw Sherlock sitting at the kitchen table staring at the petri-dishes without actually seeing them.
"Need any milk for your experiments?" he teased the younger man. He waited for a reaction, but none came.
"Sherlock! Saying hello has nothing to do with sentiment, so even you could condescend to do so!" John was really getting angry now. This hadn't been the best of days so far and the powder keg in the ex-army man only needed a little spark to set it off.
He put down the shopping bag on the counter slightly more violently than would have been necessary, risking another split carton of milk. Turning around, he shouted: "Sherlock! I am really, really pissed off…."
His voice trailed off when he noticed the expression on Sherlock's face. Was that … fear? No, impossible. There was nothing that could really worry the Consulting Detective. Due to his analytical mind and his denial of emotions in general there was nothing that John could think of that would scare Sherlock Holmes. Still, there was something in his expression that John had never seen before.
"Sherlock, what's wrong?"
The addressed person finally looked at John, having slipped on his usual mask of indifference again.
"Nothing", was his brisk reply. He suddenly pushed the chair back, stood up and left the kitchen.
"Don't you dare touch my petri-dishes!" he yelled, with a sudden change of emotion, then crossed the living-room and a second later John heard the door to Sherlock's room being slammed.
The shorter of the flatmates stood at the kitchen counter, flabbergasted. Over the time John had become used to Sherlock's changing moods, but this was strange. The exclamation about not touching the experiments had almost sounded panic-stricken. Also, Sherlock knew John wouldn't mess around with his flatmate's more or less scientific stuff. John's glance fell on the kitchen table. The petri dishes had been rearranged, most of them piled into towers. However, one of them was placed right in front of where Sherlock had just been sitting. Was that probably the cause of Sherlock's strange behaviour?
John walked around the table and examined the item closely, leaning over the kitchen table and yet refraining from touching it. There was mould growing in shades of orange and yellow in a couple of colonies. John didn't know what species it could be. He shrugged. He would have to ask Sherlock what, if anything at all, made this container so special that it hadn't been piled like the others and hadpossibly caused a pretty peculiar reaction from its owner.
Before turning away, John threw a last quick glance at the petri dish – and froze: the pattern of the colonies looked like a death's head. He hadn't seen it when looking at it from little distance. Maybe he only imagined it, but going by Sherlock's odd behaviour he had seen it, too, and it had scared him!