In the novel The Big Four, James is an under-footman employed by Abe Ryland at his rented country house at Hatton Chase. In reality he was a persona played by Claud Darrell, "Number 4" of "The Big Four".
Hastings, who had infiltrated Ryland's staff undercover, at first dismissed James as being unimportant, and unlikely to have any connection with "The Big Four" syndicate which he was supposed to be investigating. Later Hastings and Poirot were lured to a quarry nearby and met Ryland who threatened them with death. The tables were turned and those at the quarry were arrested by Japp and his men whom Poirot had arranged to surround the place. However the Ryland at the quarry turned out to be James in disguise, playing out a wager made among the domestic staff that he could realistically pass himself off as Ryland. From this, Poirot surmised that James was yet another of the personas adopted by "Number 4" (Claud Darrell), a master of disguise and chief "hitman" of the "Big Four" syndicate.