The Secret Adversary
Inspector Japp is also briefly mentioned in the Tommy and Tuppence book "The Secret Adversary" (1922); his card is brought to Julius Hersheimmer at the end of chapter five. In chapter seventeen of "The Murder of Roger Ackroyd" (1926), Japp is mentioned by a police superintendent to Poirot as having asked after him. Japp is mentioned by Colonel Weston in "Evil Under the Sun" (1941), the next book in the Poirot series after his final appearance. Japp is also mentioned in the novel "Taken at the Flood" (1948) by Superintendent Spence during a conversation with Hercule Poirot.