In the short story The Cornish Mystery, Dr Adams is the doctor of Mrs Pengelley. He attended to her when she complained that she was frequently sick after meals. He diagnosed gastritis but Mrs Pengelley could tell that he was puzzled and uneasy. He was always changing the medicine but nothing did any good.
With Poirot and Hastings, Adams was far more insistent. Hastings observed that he was "the typical red-faced country doctor of fiction" but at the hint of their errand to inquire about the possibility that Mrs Pengelley had been poisoned, "his red face turned purple". He stood by his diagnosis of gastritis and claimed that anything else was "gossip" from "a lot of scandal-monering old women". All the same, Hastings noted that he was more perturbed than he cared to admit and Poirot remarked that Adams had an easy mind. This unease came to the surface at the trial of Edward Pengelley when Adams admitted that the symptoms of arsenic poisoning might easily be mistaken for gastritis.
In the 1990 ITV film adaptation of The Cornish Mystery, Dr Adams is portrayed by Derek Benfield. The portrayal is highly faithful to the original, with many of his lines from the original text being used in the dialogue. If anything, Adams is portrayed as even more stubborn than in the original. Adams continues to insist on his diagnosis of gastritis, even during the trial. He contends that the symptoms of gastritis and arsenic poisoning are the same, even though the judge reminds him that this is contradicted by the home office expert.