Like the 1939 movie version of "The Wizard of Oz," Rachel Joyce's new novel, "Miss Benson's Beetle," starts out in black and white and then opens up into glorious Technicolor.

In 1950, World War II is over but England remains grim and gray, with food and goods still rationed and everybody ground down. "Streets were lined with broken buildings … you could go miles on the bus and not see a flower. Or blue sky."

Middle-aged schoolteacher Margery Benson is chafing at her dreary life, which feels like it's over before it has even begun. She pictures herself as "a beetle in a killing jar, dying slowly."

On the day that her students pass around a mocking cartoon depicting her as a lumpy woman with a nose like a potato and feet like planks, she has finally had enough.

She walks out of the classroom where she is teaching the loathed domestic sciences, inexplicably steals a fire extinguisher and a pair of boots from the teachers' lounge, gets on a bus, and heads off into a new life.

Many of Joyce's protagonists are middle-aged, unhappy characters, good people who are leading bland lives that hide intense psychic pain. They rashly plunge into some kind of irrational but liberating behavior — often, some sort of quest. Joyce's first novel, "The Unlikely Pilgrimage of Harold Fry," found the protagonist heading out from his home in the south of England to mail a letter — and then, instead, walking the letter to its destination in the north of England.

"Miss Benson's Beetle" follows this pattern in a general way, but it feels larger than Joyce's other books — more expansive, swashbuckling, a wild adventure. It is the best so far of her novels, and the most inspiring.

As a girl, the last bright moment in Margery Benson's life was the afternoon her gentle father introduced her to a book of amazing creatures — the Loch Ness Monster, the South African quagga, the golden beetle of New Caledonia. At the sight of the beetle, "her insides gave a lurch. … It was as if Nature had taken a bit of jewelry and made an insect instead."

And so on the day that she steals the boots, Margery decides the hell with the domestic sciences; she will sail to New Caledonia and find that beetle.

It's a preposterous idea. Not only is the journey long and dangerous but the beetle most likely doesn't exist. But off she goes, with a paid companion she finds through the classified ads. Enid Pretty is feisty and tough, a blond woman in high-heeled boots who irritates Miss Benson by calling her "Marge." Somewhere along the way, Enid acquires a dog, which strains their relationship even more.

At the heart of the story is the slow, unlikely friendship that builds between the two women and how that friendship enables them both to grow stronger, more capable and more self-reliant. And if this sounds hokey, well, it's not. It's thrilling.

New Caledonia, the women find, is the opposite of postwar England, a lush, flower-filled, intoxicating place. "A golden-white beach on one side, palm trees with tops like feather hats. … Everything smelled of pine and frangipani. As the sun lifted, the sky flashed with bright colors. … All this newness, this strangeness. This wonder."

There are delightful flashes of humor in this novel — Margery's first attempt at sleeping in a hammock comes to mind — but this isn't a sweet book. The women don't always act honorably — they fight, they bicker, they betray each other. Secrets and hurt from their past threaten to jeopardize their present. Joyce is excellent at depicting their pain and revealing their failings, and she has no qualms about repeatedly placing her characters in harm's way.

As Margery and Enid sail across the ocean and trek up mountains, they are stalked by a man, a war-shattered soldier who has become obsessed with Margery. Where she goes, he follows. At first he's a month behind them, but as the gap begins to close, the danger grows palpable.

The closer Margery and Enid get to their goals, the tougher the obstacles. There is violence, there are harrowing scenes. The dog — oh, the dog.

The ending is not pat, nor fully happy. But it is hopeful. There is resilience, there is redemption, and there is beauty — great beauty. In Technicolor.

Laurie Hertzel is the senior editor for books at the Star Tribune. • @StribBooks

Miss Benson's Beetle

By: Rachel Joyce.

Publisher: Dial Press, 368 pages, $18 paperback.