‘LAVENDER’

a secret — one of several filmnoir tropes with which Rosen has fun. She’s the self-described wife of Irene Lamontaine, a youngish, seemingly healthy soap magnate whose recent death looks like murder. After learning of Evander’s ordeal, Pearl tracks him down and asks him to figure out what happened before Irene’s body was discovered beneath a balcony at her home.

Pearl “can trust” Evander, she reasons, because she too must conceal her sexuality.

Pearl takes Evander to the scene of the apparent crime, a mansion with lots of flowering lavender. “That’s why we call this place Lavender House,” she says, adding, “Well, and for the other reason.” The other reason? “We’re all queer,” Pearl says of the relatives, rivals and potential suspects who live there.

The residents include Irene and Pearl’s son, Henry, and his boyfriend, Cliff; and Henry’s wife-in-name-only Margo and her lover, Elsie. Did one of them kill Irene? Money, control of the company, ever-shifting alliances — all are plausible motives.

Evander is intrigued. Temporarily relieved of the urge to end his life, he takes the case and moves into Lavender House. In furtive chats with household staff and at meals during which Pearl, Henry, Cliff, Margo and Elsie trade barbs and insinuations, Evander edges closer to the truth.

This is a brisk, entertaining novel populated by characters whose dilemmas never feel contrived. In a moving scene, Evander explains the dread that comes with being vilified for your sexual orientation. In the days since vindictive former colleagues outed him, gossip is “spreading like a disease,” he says, “and I don’t know who’s going to find out next.” Minor characters are strong, too, like the coroner’s secretary who’s heard about Rosen’s troubles and aids his investigation because her granddaughter is a lesbian in a world that maligns her.

Meanwhile, Rosen’s novel is a winning homage to old-time crime fiction. In “Lavender House,” as in the Billy Wilder film “Sunset Blvd.,” a corpse is found facedown at a mansion. Rosen’s private investigator has a conspicuously injured nose, like the P.I. in Roman Polanski’s “Chinatown.” And, as in Agatha Christie novels, his fictional estate is full of housemates under suspicion.

Rosen re-energizes these tropes by placing Evander at the heart of the proceedings. Refuting an inane stereotype about gay men, he’s not to be messed with, outmuscling a violent bully in the book’s opening scene. He’s here to help those who need it — among them, San Francisco’s wrongly marginalized. Their plight is his.

RACHAEL SHANE Lev AC Rosen is author of the new thriller “Lavender House.”