Inside the cover of Mr. Doyle & Dr. Bell, by the Toronto crime-writer Howard Engel, is a quotation: "The detective is the modern knight errant. His quest, not a fair maiden in distress-not necessarily-but justice itself."
The utterance is made by Prime Minister Benjamin Disraeli when he meets Dr. Joseph Bell in Engel's enthralling new mystery. Dr. Bell has travelled south from Scotland to meet Disraeli in York. Aboard the prime-ministerial railway car, Disraeli takes a few minutes off from other matters to assure Bell that he will do his bit in the doctor's plan to rescue justice.
Did Disraeli really utter the interesting sentiment about the role of the detective, or was it fresh-minted by Engel? As we read, this question fades before the deeper one, about what is made of it in this novel. If we should want to know about Disraeli, we turn to biography, a species of history in which we can understand something of what people have done. Fiction aims higher. It aims to show what is possible, what the human condition may yet be capable of.
Engel's novel is set in 1879. Like Disraeli, Dr. Bell is a historical figure, famous at that time in Edinburgh University Medical School as a diagnostician, famous too for making astonishing inferences about his patients' lives and circumstances from trifling details of clothing, posture, and demeanour. It was he-historically-who was one of the teachers of the medical student Arthur Conan Doyle, who also appears in this story. Bell was the model for Conan Doyle's most famous creation, Sherlock Holmes. But in this story we get not the derived persona of Holmes, but the original Dr. Bell, while Doyle occupies the role that he later made famous in Dr. Watson, of assistant and foil to the detective.
By the end of the third chapter, one Graeme Lambert has solicited the help of Dr. Bell in the cause of his brother, Alan Lambert, who has been arrested for a horrible double murder of a famous operatic singer and her lover. The police have gone to a great deal of trouble and to too much expense to trace and arrest their suspect. They bring him back from America to face a trial that is a travesty. Bell and Doyle discover "no less than five-and-twenty erroneous statements of fact and false inferences from the evidence." Nonetheless, Lambert is convicted. As sentence is passed, the clock starts ticking: just three weeks to the moment when the sentence of death by hanging will be carried out.
Can Dr. Bell and Mr. Doyle, bustling among gaunt buildings of Auld Reekie, the Victorian name for smelly, smoky Edinburgh, see their way through the obscurities of the case? Among the characters in the book are: the opera singer's ex-husband, the Procurator Fiscal (Scotland's chief law officer), the Procurator's son, and policemen at different levels of the Edinburgh force.
I cannot of course say how the story turns out. I shall say merely that in the closing scenes Dr. Bell, himself accused of interfering with justice, addresses the major characters who are brought together in a single room, and confronts them with the truth.
What the modern detective does is not really to rescue, as the Disraeli of this story says, but to heal. He is a slightly otherworldly character who attends to an ugly breach in society, and mends at least some of its damage. Just as a doctor first diagnoses, and then by mysterious physic or some shocking surgery, makes better what was diseased, so too the detective first understands not just the details but the heart of the case, and then acts to confront the evil. To diagnose means (etymologically) to know thoroughly. Knowledge is power, and what doctor and detective both do is bring knowledge to bear. They must make astonishing inferences that contradict the conventional. The result is that the patterns of ordinary life, injured by disease or crime, can recover and continue. In the course of the investigation we readers are let into secrets, half guessed but not fully known.
It seems unsurprising that in Conan Doyle's stories, Holmes and Watson, pursuing desperate criminals, often found themselves in danger. Holmes himself plunged to his death in a brutal struggle with Moriarty, the Napoleon of crime, or so at least it seemed.
In the 1920s, the fashion was for crime-writers to keep their detectives immune. It is hard to imagine Agatha Christie's Miss Marple threatened by her adversaries. This convention seemed to emphasize the otherworldliness of the detective, to emphasize too the potency of knowledge. It is a convention that continues. Even in modern detective stories, it is not unusual for the most cynical of criminals, when confronted with the truth, compulsively to confess.
The tradition in nineteenth-century mysteries, reinstated by Dashiell Hammett in the 1930s, was that those who investigate evil are liable to be touched by it; at least they put their own lives in danger. In Engel's gripping tale, the quest has dangers that we realize when, early in the story, the young Conan Doyle is almost crushed by a cart.
In Engel's story, the threats to the investigators are integral to the plot. As the story unfolds, it comes to seem more and more likely that the culprit is not just some individual, frightened and fleeing from the law, not even a conspiracy of corrupt people, but a structural fault in the system of justice itself. Although people make mistakes and even sometimes confess, organizations defend themselves and we seldom hear them owning up. For individuals to confront a whole system is to risk a great deal.
Here then Howard Engel enters daring new territory for the mystery novel. He keeps the tension high while Bell and Doyle, modern knights errant, pursue what seems an increasingly quixotic search for the fault in the system of justice itself.

Keith Oatley is the author of The Case of Emily V., which like Engel's book is peopled by both historical and fictional characters.