Watson smiled reassuringly at the distressed couple, while Holmes rubbed his chin thoughtfully, expression unreadable as ever.
"And the servants heard nothing unusual?"
The husband patted his trembling wife's hand stiffly. "No, nothing. The maid had just looked in on the children, about twenty minutes earlier."
"Why so?"
"The children's na... er, our dog, Nana," the man explained, face turning pink. "She was barking furiously and couldn't be quieted. Liza took her upstairs to reassure her, before chaining her up in the garden."
Holmes's eyes narrowed. "At what time?"
"Around eight o'clock. My wife and I were attending a Christmas party. We only knew anything was wrong when Nana arrived at the door; she'd broken her chain."
"Dog had more sense than its masters," Watson murmured, low enough that only Holmes could hear.
The detective shot him a warning glance. "Pray continue, Mr. Darling," he said smoothly. "Why have you refrained from notifying Scotland Yard?"
Mr. Darling's face grew redder still, exchanging an uncomfortable look with his wife. "Because, Mr. Holmes, we feared the police would either believe us mad, or guilty of the... the abduction ourselves." He took a piece of notepaper from his pocket and unfolded it.
Watson's breath caught. Across the paper meandered a trail of inky footprints, human shaped, but as tiny and delicate as a butterfly's...
A/N: Was trying to work out when in Holmes's career this might have happened. It must have been quite late, since stuffed animals, like Michael's teddy bear, were only available in shops from 1902 onwards.