Enola Holmes is on the case, when a young porter - the boy in buttons - disappears without a trace.

Enola Holmes, the much younger sister of Sherlock and Mycroft, owns a building in the heart of 19th century London, a place she uses under pseudonyms to front for her investigative work. Employed there is a porter - Joddy, a young boy in a uniform festooned with buttons - whose even younger brother substitutes for him when he's sick. But Paddy disappears after one day at the job and Enola Holmes is alerted to this by the still ill Joddy.

Determined to find the missing porter, Enola travels to the rough part of London where the boys live and starts searching Aldgate Pump area for the missing boy. When she finds the missing buttons - but not the boy - she decides that drastic action is essential if she's to save the missing boy.