It had been for an experiment after all, the second time. There were nine candles burning in the Hannukiah, and nine digital timers propped up in front, and several full boxes of candles piled to one side.
"Glad to see you're getting some more use out of that," John said mildly.
"Cold case," said Sherlock from the sofa. "But there's nothing else—"
At that moment Sherlock's phone had buzzed, and ten minutes later they were out the door to investigate a murder in Hampstead. They had come home to colorful stalagmites of cold wax on the table, and left them there until Mrs. Hudson cleaned it up the following week. She put the candles in a drawer and the Hannukiah on the bookshelf, and John couldn't do any better because he didn't know where Sherlock had been keeping it. And Sherlock of course did nothing at all.
The third time, four months later, was the rainstorm that knocked out the electric. They stared at each other's silhouettes for a full minute before Sherlock said "Hannukiah, John."
John's memory sparked at the smell of sulfur as he struck the match. "It's actually Hannukah tonight, I think. There was, uh, a sign up at Tesco."
"A good night for a candlelit dinner, then," said Sherlock. "Good job we've got plenty to burn."