Christina McDowell was used to getting extraordinary gifts from her father, Washington lawyer Thomas Prousalis Jr. To celebrate her graduation from high school, she got a BMW. One Christmas morning, he gave her a Hermès Birkin bag. And then there was that time McDowell discovered Dad had given her $100,000 in credit card debt.

McDowell wanted to ask him about that little problem, but she didn’t know exactly where her father was, only that he would soon be assigned to a federal prison to serve a 57-month sentence for securities fraud. He was a convicted associate of Jordan Belfort, whom Leonardo DiCaprio portrayed in “The Wolf of Wall Street.”

For a young woman raised in the gold-leaf parlors of Washington, in a home just a few blocks from the Kennedys’ Hickory Hill estate, her family’s sudden disgrace and poverty ushered in an era of traumatic reevaluation. (And the Birkin bag was fake.) McDowell described that ordeal in her 2015 memoir, “After Perfect.”

Now, she’s back — and this time, it’s fictional. Sort of.

The Cave Dwellers,” McDowell’s debut novel, takes its title from a local nickname for the Capital’s oldest and wealthiest families, folks who have moved in the shadows of D.C. society since their ancestors lived in caves. These are “the aristocratic bloodlines woven into the fabric of Washington,” McDowell writes. “They only socialize within their inner circle, which is impenetrable — turning a blind eye to those who come and go on the political merry-go-round.” After reading this ruthless satire of their behavior, they probably can’t sue for slander, but they might want to beg for mercy.

The story opens with a terrifying crime that will remind locals of the 2015 D.C. Mansion Murders. A man enters a house near Rock Creek Park and ties up Mr. and Mrs. Banks, their 14-year-old daughter, Audrey, and their housekeeper. The neighbors can’t hear the screams as they’re beaten with an autographed Ted Williams baseball bat and sliced open with a vintage samurai sword. In fact, no one even notices when the house is set ablaze. “No one in Washington wants to be part of a scandal,” McDowell explains. “The consequences are fatal, socially and economically.”

With all its horror and glamour, this could be the opening of a thriller, but “The Cave Dwellers” is more interested in the bloodless crimes committed in country club dining rooms and at private school parties. While the murder investigation progresses far in the novel’s background, McDowell introduces us to other wealthy families whose teenage children attend St. Peter’s Academy, where Audrey Banks was a student. They are all deeply shaken by the murders. They all attend the group funeral at Washington National Cathedral, though no one complains that the housekeeper’s casket has been excluded from this ritzy ritual in one final act of redlining.

Of course, people grieve in different ways. Sen. Doug Wallace is so moved by the service that he ducks into the basement with his young press secretary to have sex against Helen Keller’s crypt. (Don’t worry, she reassures him, “she was blind and deaf.”) Meanwhile, Meredith Bartholomew, one of the true cave dwellers, shows her respects by critiquing the commoners’ mourning clothes.

And by “commoners,” Meredith means Betsy Wallace, that new senator’s wife. Betsy is determined to break into the upper echelons of Washington society without the requisite 12 generations stretching back to (the White side of) Thomas Jefferson’s family. Every chance encounter with anyone in the Social List of Washington — the Green Book — is an opportunity for advancement, and when those chance encounters don’t occur naturally, Betsy engineers them. Struggling to gain membership in the Washington Country Club, she “can’t remember which religion she should check on the application. . . . Should she buy a bigger diamond cross, or more Ralph Lauren?”

For its merciless humor and brazen exposure of salon secrets, “The Cave Dwellers” should join that small collection of essential Washington books. And don’t worry if you haven’t recently visited — or stormed — the Capitol. Between chapters, McDowell provides potted explanations of Embassy Row, Washington Life Magazine, Cafe Milano — everything you need to follow along this new-old vanity fair.

After all, this is an author who knows her victims’ antique attitudes and traditions as well as Marjorie Merriweather Post knew her china settings. The pages are packed with more high-class brand names than a copy of Town & Country. (I learned that the Kellogg Collection has nothing to do with breakfast cereal.) But the members of this rarefied tribe never flaunt their wealth; they don’t need to. They know just where to summer and where to winter. They’re so controlled, so concerned with propriety that when they have sex, they sound like they’re “tasting apple pie for the first time.”

But if the melody of “The Cave Dwellers” is satire, its baseline is sorrow. That sometimes produces a strange clashing of tones, as though the author is still recovering from her own trauma while mocking her old peers. The children of these Washington blue bloods live in an intoxicating and imprisoning haze. They fly private jets to the Alps and snort coke at parties guarded by their parents’ security details. Except for the anxiety, the loneliness, the parental pressure and the sexual humiliation, it’s a blast. They will never grow up, McDowell writes, “outside of make-believe, invisible boundaries keeping them separate and apart from the inevitable leaking whispers of failure — deaf to the screams of financial suffocation.”

But Bunny, the 17-year-old daughter of one of the most august families, starts to suspect that something is seriously amiss in their tastefully appointed realm. A spore of shame has infected her conscience and awakened her to the possibility that her position rests upon centuries of exploitation. Alerted to the existence of White privilege, she suddenly sees how it deconstructs the justification for every advantage she enjoys. Was Audrey Banks’s murder really a random act of violence, Bunny wonders, or was it a long-simmering act of revenge, the beginning of the end for the cave dwellers?

Ron Charles writes about books for The Washington Post and hosts TotallyHipVideoBookReview.com.

The Cave Dwellers

By Christina McDowell

Scout Press. 352 pp. $28