“Tangerine,” Christine Mangan’s first novel, opens with three men pulling a corpse from the waters off Tangier, wondering what kind of birds pecked out its eyes and whether dead bodies weigh more than living ones. But then we get to the hook that really propels the story forward. The unnamed narrator tells us: “Of course, only the first bit is true — the rest I have simply imagined.”

“Tangerine,” by Christine Mangan (Ecco)

It won’t be until halfway through the novel that we learn whose body this is. It won’t be until the end that we know who is sitting alone in an asylum or nursing home across the Strait of Gibraltar and ruminating on the deceased. It’s clearly going to be one of Mangan’s two narrators: Alice Shipley or Lucy Mason. But which one? Between the prologue and the epilogue, the story is told in alternating chapters by each woman.

It’s 1956, a year after Lucy and Alice have left Bennington College in Vermont. They were roommates and close friends, despite their difference in backgrounds. Alice is a wealthy Brit, Lucy a poor Vermonter on scholarship. They share the trauma of having lost their parents, Lucy as a young girl, Alice more recently.

But neither is a reliable narrator — that’s clear early on. Alice is emotionally fragile and was nearly institutionalized after her parents’ death in a house fire, a blaze that Alice may (or may not) have caused. Lucy is stronger than steel, but she’s also a lying sociopath. She’s the sort of female predator who once upon a time gave pulp novels dramatic covers and Judi Dench an Oscar nomination (“Notes on a Scandal”).

Lucy and Alice’s friendship implodes their senior year at college and, for a variety of reasons, Alice hopes never to see her roommate again. She returns to London, and Lucy decamps with her lone suitcase to Manhattan. Back in Britain, Alice marries John McAllister, a fellow whose work brings him to Tangier. A year later, Lucy shows up unannounced at their front door in North Africa — and we’re off.

Rather like a tennis match, Alice and Lucy volley back and forth, each telling her side of what occurred after Lucy’s unexpected arrival in Morocco. And, like a good tennis match, the salvos grow more intense. Lucy is a chameleon who makes Patricia Highsmith’s Tom Ripley look talentless when it comes to reinvention. She’s a force to be reckoned with. Alice, it would seem on the surface, is going to be easy prey. But as emotionally frail as she is, she still rallies just enough to keep the match close and gives us hope for an upset.

The author Christine Mangan (Casey Carsello)

Occasionally, the story’s momentum is slowed by Mangan’s enthusiastic attempts to turn the novel into a threesome, with Tangier as its third character. “Only Tangier knew,” she writes, “and I suspected she would keep her secrets.” And later: “He was with a woman he had loved, for better or for worse, and whatever that love had meant to him, he would be with her, Tangier, for the rest of time.”

Moreover, sometimes the two women sound so similar that they are difficult to distinguish. They both have trouble drinking hot mint tea from glass cups instead of porcelain with handles, and they both “wrench” their shoulders in acts of violence. They both ponder the nuances of the words they use (tourist vs. traveler), and sometimes take their interest in vocabulary to the edge of parody: “I mused briefly over the fact that ‘thank you’ and ‘no thank you’ were so closely related — the difference of a word added to the latter.”

Still, these are small distractions. The lying, the cunning, and the duplicity are so very mannered that it’s chilling. Rich in dread, the foreboding positively drips from every page of this one.

Chris Bohjalian just published his 20th novel, “The Flight Attendant.”

tangerine
A Novel

By Christine Mangan

Ecco. 308 pp. $26.99