Prompt from YoughaltheJust: Icy streets.
"I see the streets are icy out there today, Watson," Holmes commented as I came in, melted snow dripping from my coat.
"Not a deduction worthy of your abilities. A single minute outside could have told you that," I grumbled, for the morning had been cold and unpleasant. I stumbled over to the table, eager to have a seat and rest my weary legs, and was exceedingly grateful to find Mrs Hudson had left a pot of tea waiting for me.
As I sipped at my mug, slowly warming from the inside, Holmes must have noticed my regaining good cheer, for he continued on, "As it happens, I have not been outside at all this morning. My deduction came entirely from your coat."
"My coat?"
"And your trouser-leg. The knees, I have told you before, are most revealing. In your case, Watson, the knee of your trouser shows that you have slipped and fallen, and the marks on your coat sleeve show where you have struggled to regain your feet. There is also a light dusting of ice on the brim of your hat where it brushed against the wall. Clearly, the ice on the street was enough for you to lose your footing and fall, despite your cane. When you tried to regain your feet, the ice brought you down again. Nothing could be plainer."
"Most impressive, my friend." I toasted him with my teacup. "Yet there was a further step you missed."
He raised an eyebrow inquisitively.
"That any man who had been out on icy streets all morning would want a hot cup of tea when he came in!"