What if you saw something suspicious and did nothing? ‘The Lodger’ posits a consequence.

Tesla shares slide on news of Walmart suing over solar-panel fires

“If you see something, say something.” But what if you see something or suspect something and do nothing. What then?

After every murderous atrocity, the police, news media and, these days, our White House tweeter-in-chief reflexively speculate about the motives and psychology of the perpetrator. Might there have been warning signs or red flags? Half the time, he — it is usually a he — is described as quiet, a loner, maybe just a bit odd, not at all the kind of person to do something horrific. Surely, though, some family members, friends or neighbors must have occasionally felt uneasy or had their suspicions?

(Chicago Review) In 1913 Marie Belloc-Lowndes addressed this haunting question in the one novel she is remembered for: “The Lodger.” Based on the Jack the Ripper murders of 1888 — which, incidentally, began in late August — it remains even now a brilliant work of psychological suspense. In its pages, however, Belloc-Lowndes focuses less on a Ripper-like killer called “The Avenger than on an ordinary, middle-aged woman named Mrs. Bunting.

[ Johnston McCulley dreamed up Zorro 100 years ago. The masked avenger is still a thrill. ]

Once a devoted, punctilious maid in various upper-class households, Ellen Bunting now misses the security of her old life. After marrying a widowed butler, she and Mr. Bunting left service, hoping to make their way by leasing a house off London’s Marylebone Road and renting upstairs rooms to lodgers. Things haven’t worked out and, as the novel opens, the Buntings are on the verge of starvation. “Never, never had she felt so hopeless, so — so broken as now. Where was the good of having been an upright, conscientious self-respecting woman all her life long, if it only led to this utter, degrading poverty and wretchedness?” Virtually penniless, the couple don’t know where to turn, when Mrs. Bunting answers a tremulous, uncertain knock at the front door:

“On the top of the three steps . . . stood the long, lanky figure of a man, clad in an Inverness cape and an old-fashioned top hat. He waited for a few seconds blinking at her, perhaps dazzled by the light of the gas in the passage. Mrs. Bunting’s trained perception told her at once that this man, odd as he looked, was a gentleman, belonging by birth to the class with whom her former employment had brought her in contact.”

Might he see the rooms for rent? At that question, Mrs. Bunting feels her heart leap. “It seemed too good to be true, this sudden coming of a possible lodger and of a lodger who spoke in the pleasant, courteous way and voice which recalled to the poor woman her happy, far-off days of youth and of security.”

Surprisingly, the soft-spoken gentleman carries nothing but a small leather handbag, about which he seems strangely anxious. Rather than go through the tedium of supplying references, Mr. Sleuth — for such is his odd name — offers instead to pay in advance, and to pay extra for that matter, if Mrs. Bunting will keep her other rooms unoccupied. Weary in body and soul, he yearns for a haven of solitude and peace. Still, Mr. Sleuth grows positively excited over a stove in one of the rooms. “I am a man of science,” he explains. “I make, that is, all sorts of experiments, and I often require the — ah, well, the presence of great heat.”

The new lodger turns out be a teetotaler and vegetarian, utterly repulsed by drink and meat. Most days, he studies the Bible for hours, often murmuring verses aloud: “A strange woman is a narrow gate. She also lieth in wait as for a prey. . . .” What’s more, the eccentric Mr. Sleuth likes to take long walks in the middle of the night and then, right after his return home, immediately begin one of his private experiments.

At first, Mrs. Bunting worries about her “perfect” lodger catching a chill on his nocturnal excursions — how would she and her husband survive without him and his shiny new sovereigns? Worse still, he might encounter the insane killer who leaves a triangular gray card inscribed “The Avenger on the mutilated bodies of his victims. Day after day, the morning newspapers report this shadowy fiend’s latest outrage, theorize about his identity and, not least, drive the plot inexorably along. Joe Chandler, a young detective assigned to the case as well as a friend of the family, regularly stops by for a cup of tea, often asking about Mr. Bunting’s almost 18-year-old daughter, Daisy. Because she and her stepmother don’t get on well, Daisymainly lives with an old aunt in the country. But eventually she arrives for a long visit.

[ ‘Ashenden’: the perfect late summer escape read, and a classic ]

Since its publication as a novel, “The Lodger” has been made into a stage play, filmed several times (in 1926 by a young director named Alfred Hitchcock), and even turned into an opera. One can see why. There are, essentially, only five characters, most of the action takes place in the Buntings’ house, and Mr. Sleuth and Mrs. Bunting are roles to die for. So to speak.

As time goes by, Mrs. Bunting grows ever fonder, ever more protective of her reclusive lodger — he is so well-mannered, so appreciative of her attentiveness to his needs. Nonetheless, she eventually notices that he is always out on the nights when the Avenger strikes. As her suspicions increase, so does her mental distress. Mr. Sleuth has saved the Buntings from ruin. Could this courtly gentleman really be capable of brutal savagery? Soon, Mrs. Bunting is making excuses for her lodger’s unsettling behavior, even lying about his movements to Joe Chandler. And then Mr. Bunting starts to have his own suspicions. Meanwhile, Mr. Sleuth has taken notice of the pretty, vivacious Daisy.

Marred only by an incongruous few pages toward the end, “The Lodger” remains an unputdownable study of moral indecision. Being in Mrs. Bunting’s place today, would you or I have acted any differently?

Michael Dirda  reviews books each Thursday in Style.

THE LODGER By Marie Belloc-Lowndes

Chicago Review Press. Paperback, 252 pp. $14.95