For a moment, he was obscured by the Havana night. It was as if he were invisible, as he had been before coming to Cuba, in the midst of revolution. Then a burst of floodlights illuminated him: William Alexander Morgan, the great Yankee comandante. He was standing, with his back against a bullet-pocked wall, in an empty moat surrounding La Cabaña—an eighteenth-century stone fortress, on a cliff overlooking Havana Harbor, that had been converted into a prison. Flecks of blood were drying on the patch of ground where Morgan’s friend had been shot, moments earlier. Morgan, who was thirty-two, blinked into the lights. He faced a firing squad.

The gunmen gazed at the man they had been ordered to kill. Morgan was nearly six feet tall, and had the powerful arms and legs of someone who had survived in the wild. With a stark jaw, a pugnacious nose, and scruffy blond hair, he had the gallant look of an adventurer in a movie serial, of a throwback to an earlier age, and photographs of him had appeared in newspapers and magazines around the world. The most alluring images—taken when he was fighting in the mountains, with Fidel Castro and Che Guevara—showed Morgan, with an untamed beard, holding a Thompson submachine gun. Though he was now shaved and wearing prison garb, the executioners recognized him as the mysterious Americano who once had been hailed as a hero of the revolution.

It was March 11, 1961, two years after Morgan had helped to overthrow the dictator Fulgencio Batista, bringing Castro to power. The revolution had since fractured, its leaders devouring their own, like Saturn, but the sight of Morgan before a firing squad was a shock. In 1957, when Castro was still widely seen as fighting for democracy, Morgan had travelled from Florida to Cuba and headed into the jungle, joining a guerrilla force. In the words of one observer, Morgan was “like Holden Caulfield with a machine gun.” He was the only American in the rebel army and the sole foreigner, other than Guevara, an Argentine, to rise to the army’s highest rank, comandante.

After the revolution, Morgan’s role in Cuba aroused even greater fascination, as the island became enmeshed in the larger battle of the Cold War. An American who knew Morgan said that he had served as Castro’s “chief cloak-and-dagger man,” and Time called him Castro’s “crafty, U.S.-born double agent.”

Now Morgan was charged with conspiring to overthrow Castro. The Cuban government claimed that Morgan had actually been working for U.S. intelligence—that he was, in effect, a triple agent. Morgan denied the allegations, but even some of his friends wondered who he really was, and why he had come to Cuba.

Before Morgan was led outside La Cabaña, an inmate asked him if there was anything he could do for him. Morgan replied, “If you ever get out of here alive, which I doubt you will, try to tell people my story.” Morgan grasped that more than his life was at stake: the Cuban regime would distort his role in the revolution, if not excise it from the public record, and the U.S. government would stash documents about him in classified files, or “sanitize” them by concealing passages with black ink. He would be rubbed out—first from the present, then from the past.

The head of the firing squad shouted, “Attention!” The gunmen raised their Belgian rifles. Morgan feared for his wife, Olga—whom he had met in the mountains—and for their two young daughters. He had always managed to bend the forces of history, and he had made a last-minute plea to communicate with Castro. Morgan had believed that the man he once called his “faithful friend” would never kill him. But now the executioners were cocking their guns.

THE FIRST TRICK

When Morgan arrived in Havana, in December, 1957, he was propelled by the thrill of a secret. He made sure that he wasn’t being followed as he moved surreptitiously through the neon-lit capital. Advertised as the “Playland of the Americas,” Havana offered one temptation after another: the Sans Souci night club, where, on outdoor stages, dancers with frank hips swayed under the stars to the cha-cha; the Hotel Capri, whose slot machines spat out American silver dollars; and the Tropicana, where guests such as Elizabeth Taylor and Marlon Brando enjoyed lavish revues featuring the Diosas de Carne, or “flesh goddesses.”

Morgan, then a pudgy twenty-nine-year-old, tried to appear as just another man of leisure. He wore a two-hundred-and-fifty-dollar white suit with a white shirt, and a new pair of shoes. “I looked like a real fat-cat tourist,” he later joked.

But, according to members of Morgan’s inner circle, and to the unpublished account of a close friend, he avoided the glare of the city’s night life, making his way along a street in Old Havana, near a wharf that offered a view of La Cabaña, with its drawbridge and moss-covered walls. Morgan paused by a telephone booth, where he encountered a Cuban contact named Roger Rodríguez. A raven-haired student radical with a thick mustache, Rodríguez had once been shot by police during a political demonstration, and he was a member of a revolutionary cell.

Most tourists remained oblivious of the many iniquities of Cuba, where people often lived without electricity or running water. Graham Greene, who published “Our Man in Havana” in 1958, later recalled, “I enjoyed the louche atmosphere of Batista’s city and I never stayed long enough to become aware of the sad political background of arbitrary imprisonment and torture.” Morgan, however, had briefed himself on Batista, who had seized power in a coup, in 1952: how the dictator liked sitting in his palace, eating sumptuous meals and watching horror films, and how he tortured and killed dissidents, whose bodies were sometimes dumped in fields, with their eyes gouged out or their crushed testicles stuffed in their mouths.

Morgan and Rodríguez resumed walking through Old Havana, and began a furtive conversation. Morgan was rarely without a cigarette, and typically communicated through a haze of smoke. He didn’t know Spanish, but Rodríguez spoke broken English. They had previously met in Miami, becoming friends, and Morgan believed that he could trust him. Morgan confided that he planned to sneak into the Sierra Maestra, a mountain range on Cuba’s remote southeastern coast, where revolutionaries had taken up arms against the regime. He intended to enlist with the rebels, who were commanded by Fidel Castro.

The name of Batista’s mortal enemy carried the jolt of the forbidden. On November 25, 1956, Castro, a thirty-year-old lawyer and the illegitimate son of a prosperous landowner, had launched from Mexico an amphibious invasion of Cuba, along with eighty-one self-styled commandos, including Che Guevara. After their battered wooden ship ran aground, Castro and his men waded through chest-deep waters, and came ashore in a swamp whose tangled vegetation tore their skin. Batista’s Army soon ambushed them, and Guevara was shot in the neck. (He later wrote, “I immediately began to wonder what would be the best way to die, now that all seemed lost.”) Only a dozen or so rebels, including the wounded Guevara and Castro’s younger brother, Raúl, escaped, and, exhausted and delirious with thirst—one drank his own urine—they fled into the steep jungles of the Sierra Maestra.

Morgan told Rodríguez that he had been tracking the progress of the uprising. After Batista mistakenly declared that Castro had died in the ambush, Castro allowed a Times correspondent, Herbert Matthews, to be escorted into the Sierra Maestra. A close friend of Ernest Hemingway, Matthews longed not merely to cover world-changing events but to make them, and he was captivated by the tall rebel leader, with his wild beard and burning cigar. “The personality of the man is overpowering,” Matthews wrote. “Here was an educated, dedicated fanatic, a man of ideals, of courage.” Matthews concluded that Castro had “strong ideas of liberty, democracy, social justice, the need to restore the Constitution.” On February 24, 1957, the story appeared on the paper’s front page, intensifying the rebellion’s romantic aura. Matthews later put it this way: “A bell tolled in the jungles of the Sierra Maestra.”

Yet why would an American be willing to die for Cuba’s revolution? When Rodríguez pressed Morgan, he indicated that he wanted to be both on the side of good and on the edge of danger, but he also wanted something else: revenge. Morgan said that he had an American buddy who had travelled to Havana and been killed by Batista’s soldiers. Later, Morgan provided more details to others in Cuba: his friend, a man named Jack Turner, had been caught smuggling weapons to the rebels, and was “tortured and tossed to the sharks by Batista.”

Morgan told Rodríguez that he had already made contact with another revolutionary, who had arranged to sneak him into the mountains. Rodríguez was taken aback: the supposed rebel was an agent of Batista’s secret police. Rodríguez warned Morgan that he’d fallen into a trap.

Rodríguez, fearing for Morgan’s life, offered to help him. He could not transport Morgan to the Sierra Maestra, but he could take him to the camp of a rebel group in the Escambray Mountains, which cut across the central part of the country. These guerrillas were opening a new front, and Castro welcomed them to the “common struggle.”

Morgan set out with Rodríguez and a driver on the two-hundred-and-seventeen mile journey. As Aran Shetterly details in his incisive biography “The Americano” (2007), the car soon arrived at a military roadblock. A soldier peered inside at Morgan in his gleaming suit, the only outfit that he seemed to own. Morgan knew what would happen if he were seized—as Guevara said, “in a revolution, one wins or dies”—and he had prepared a cover story, in which he was an American businessman on his way to see coffee plantations. After hearing the tale, the soldier let them pass, and Morgan and his conspirators roared up the road, up into the Escambray, where the air became cooler and thinner, and where the three-thousand-foot peaks had an eerie purple tint.

Morgan was taken to a safe house to rest, then driven to a mountainside near the town of Banao. A peasant shepherded Morgan and Rodríguez through vines and banana leaves until they reached a remote clearing, flanked by steep slopes. The peasant made a birdlike sound, which rang through the forest and was reciprocated by a distant whistle. A sentry emerged, and Morgan and Rodríguez were led to a campsite strewn with water basins and hammocks and a few antiquated rifles. Morgan could count only thirty or so men, many of whom appeared barely out of high school and had the emaciated, straggly look of shipwreck survivors.

The rebels regarded Morgan uncertainly. Max Lesnik, a Cuban journalist in charge of the organization’s propaganda, soon met up with the group, and recalls wondering if Morgan was “some kind of agent from the C.I.A.”