The Notting Hill Mystery begins in London, where the wife of the sinister Baron R__ dies after drinking from a bottle of acid, apparently while sleepwalking in her husband's home laboratory. It looks like an accident, until insurance investigator Ralph Henderson learns that Baron R__ took out numerous life insurance policies on his wife. As Henderson investigates the case, he discovers not one, but three murders. Presented as Henderson's evidential findingsdiary entries, family letters, chemical analysis reports, interviews with witnesses, along with a crime scene mapthe novel displays innovative techniques that would not become common features of detective fiction until the 1920s.