The fourth floor of the Emerald Arch Apartments was nearly identical to the third. Light stumbled meekly out of the dirty oil lamps, testing the floor without really diving down to brighten it. Jackaby hastened to 412 and knocked loudly.

“What are we looking for, exactly?” I whispered to my employer as we waited. I could hear the shuffling of motion from within the room.

“I don’t know,” answered Jackaby, “but I’m excited to find out, aren’t you?”

The door opened to a middle-aged man in an undershirt, pressed trousers, and suspenders. He held a damp towel, and daubs of shaving cream clung around the corners of his jawline. “Yes?” he said.

Jackaby looked the man up and down. “No, sorry. Wrong room,” he declared. “You’re clearly just a man.” With no further explanation, he left the confused fellow to his morning.

Jackaby rapped firmly on 411, and a woman answered. She wore a clean, simple, white dress buttoned neatly up to her neck, and her red hair was tied back in a prim bun. “Hello? What is it? I already told the last one that I didn’t see a thing.” Her accent was distinctly Irish, and edged with quiet annoyance.

“Simply a woman,” said Jackaby after another cursory examination. “No use. My apologies.” He turned on his heel and advanced toward number 410.

The woman, having been far less satisfied with the encounter than Jackaby, came out of her room. “And just what do you mean by that?” she demanded.

I did my very best to blend into the wallpaper as she stalked after the detective. Charlie, I noticed, had taken a keen interest in the points of his well-polished shoes.

“Simply a woman?” she repeated. “Nothing simple about it! I’ve had enough of the likes of you, going on about the weaker sex, and such. Twig like you, care to see who’s weaker?”

Jackaby called backward without looking behind him, “I mean only that you’re of no use at this time.”

Charlie shook his head.

The woman bristled. “I am an educated woman, a nurse, and a caregiver! How dare you . . .”

Jackaby turned at last. “Madam, I assure you, I meant only that you are not special.”

I cupped a palm over my face.

The woman reddened several shades. Jackaby smiled at her in what I’m certain he felt was a reassuring and pleasant manner following a reasonable explanation. He seemed prepared to let the whole thing wash away as a friendly misunderstanding. What he was not prepared for, apparently, was to be socked in the face.

It was not a ladylike swat or symbolic gesture. The force of it actually spun the detective halfway around, and his trip to the ground was interrupted only briefly by the wall catching him on the ear on the way down.