The Dressmaker's Doll — Agatha Christie

Previously published in the print anthology The Witness for the Prosecution and Other Stories.

Alicia Coombe manages her very smart dressmaking business with the help of her young assistant, Sybil. One day, a doll appears in the shop -- a floppy, long-legged doll that sits itself on the best sofa. But where did it come from, and why does it appear to watch them?