An ability to suspend disbelief is useful when reading fantasy or science fiction. But sometimes literary fiction requires this, as well, as a character might undergo a not entirely convincing transformation. Take, for instance, a budding poet who morphs into a Marxist militant. That's the very nearly implausible trajectory of character Sam Westergard in Ryan McIlvain's second novel, "The Radicals," which otherwise hauntingly depicts the devastation that results from according ideology precedence over human life.

Narrator Eli makes Sam's acquaintance in a class on Marxist theory at a New York college. They become tennis buddies ("I couldn't have known I was standing across the net from a murderer, and neither could he"). As Eli narrates the book, he looks back affectingly on their subsequent friendship and their involvement in political violence.

Eli is resigned to what happened and is remorseful, but he is also pitifully given to imagining alternative scenarios in which he and Sam shun violent action.

Because Sam's metamorphosis from poet to activist occurs offstage (he reads a few books Eli lends him), it comes across as a perfunctory treatment of a major plot development. At least McIlvain has the good sense not to plunge him into subversive behavior right away. Though galvanized, Sam initially remains moderate; at a weeklong protest in Phoenix over plans to foreclose on the house of a woman who has lost her job after her company was acquired by the energy giant Soline, he helps secure a compromise offer from the bank.

"Sienna on darker sienna, burnt umber, ocher, a riot of reddish browns, a vast layer cake of them, and the aerial effect stretching back and back through the dipping receding endless wedges of canyon." That's the Grand Canyon, which Eli and his musician girlfriend, Jen, visit on the drive back to New York from Phoenix, and one of several passages in which McIlvain's rich prose captures the polychromatic splendor of nature.

Back in New York, Sam and his girlfriend, Alex, an unnervingly militant socialist, have no time for nature. Their focus is on bringing together fellow radicals in a communal house. With that accomplished, Sam begins plotting against Soline CEO Larry Bosch.

The Radicals, by Ryan McIlvain

Meanwhile, Eli, whose revolutionary fervor has ebbed, still feels inexorably drawn to — or maybe responsible for — Sam.

Soon, a chastened Eli will have this to say: "I regret Sam's projection that incubated and grew, with our help, and became flesh and blood."

Rayyan Al-Shawaf is a writer and book critic in Lebanon. He reviews for many publications in the United States and Canada.

The Radicals
By: Ryan McIlvain.
Publisher: Hogarth, 271 pages, $26.