This year, Firestone, the iconic American tire company, has lost dozens of employees to Ebola. These are certainly trying times for the 114-year-old tire maker, which is owned by the Japanese conglomerate Bridgestone and has operated its 185-square-mile rubber plantation—the world’s largest—in Liberia since 1926. But while Firestone has been commended for its efforts to fight the outbreak, it is under scrutiny for a far more more troubling period of its recent history in that country.

“Firestone and the Warlord,” a gripping PBS Frontline and ProPublica investigation that debuted yesterday, exposes the company’s secret dealmaking with a powerful Liberian strongman.

The multi-year investigation, which draws from declassified diplomatic cables and court documents, paints a disturbing portrait of a corporation that, when caught in the crosshairs of a brutal civil war, apparently made some bad choices in the name of business. (Firestone defends its actions, saying that it was focused on the well-being of its employees.) The controversy surrounds Firestone’s relationship with one of the most infamous warlords of the 20th century: Charles Taylor.

The biography of Taylor, a brutal guerrilla leader and former Liberian president, currently serving a 50-year sentence for war crimes, offers one of the stranger stories in post-colonial Africa. A charismatic figure, educated at a small American university in Massachusetts, Taylor landed a top job in the Liberian government before fleeing the country after being accused of embezzlement in the 1980s. Tracked down in the U.S., Taylor was sent to a Massachusetts jail—where he somehow escaped. (The story of that escape is one of the great mysteries surrounding a man whose life seems utterly defined by them.)

Taylor went to Mexico and then to Libya, where he trained under Muammar Gaddafi. Soon, Taylor, hardened by military training and harboring mighty ambitions, was back in Liberia, raising a rebel army of his own.

For many of Firestone’s years in Liberia, the country had not been a particularly stable place. There were occasional coups, leaders came and went. But Firestone, the country’s largest multinational employer, managed to weather this turmoil, apparently, with little disruption: Its rubber-tapping operations continued apace and its ex-pat managers enjoyed life on a plantation with grand homes and a 9-hole golf course.

But by June 1990, Taylor’s band of fighters—notoriously comprised of children, many of whom were on drugs, in costume, and/or wielding AK-47s—approached Firestone’s plantation with demands for food, money and cars. Firestone employees were killed and management fled.

It’s what happened next that, according to the Frontline and ProPublica investigation, is especially troubling. With Firestone’s top managers gone, Taylor and his forces assumed control of the plantation and made it an operations base. The company was keen to get it back, or at least resume operations there, according to the investigation. The site provided 40% of U.S. latex supply. Within months, Firestone began discussions with Taylor. At the time, Taylor had no formal power, but he controlled much of the country, a vast territory that many had taken to calling “Taylorland.” He had also cemented his reputation as a ruthless warlord, a status that made him a controversial negotiating partner both within the company and beyond. Members of the U.S. diplomatic corps, for instance, had warned against working with Taylor.

Taylor was keen for Firestone to resume operations too: he saw the company as a source of credibility and cash. He publicly scolded Firestone for abandoning the country, and privately (in a deal struck with Firestone higher-ups in the jungle, the investigation reveals), welcomed the tire maker back on the condition that it fire a top manager and “pay taxes” in Taylorland. Firestone paid $2.3 million to the guerrilla leader, according to evidence unearthed by the Frontline/ProPublica team, which found a schedule of payments—including so-called “income tax” and “social security pension and benefits.” The bill for this had been typed out and signed on the guerrilla leader’s stationery. During the early ’90s, a period in which Firestone and Taylor’s rebel army cohabited the plantation, the warlord continued to use Firestone’s assets as he pleased. In October 1992, the plantation became a staging ground for “Operation Octopus,” Taylor’s final, bloody drive to power: the invasion of Monrovia.

Certainly, Firestone was in a tricky position. Liberia had no formally recognized government and the company’s assets—not to mention its workforce of 8,000 Liberians—lay in Taylor’s territory. Momentum was perhaps on his side. The choice was to do business with Taylor or to do no business at all, and the company defends its actions as the hard, but necessary steps taken to care for the employees and investments it had in country.

By Taylor’s admission in war crimes proceedings at The Hague, Firestone’s return to Liberia very much fueled his rise and reign of terror. In the end, Firestone employees suffered as well: After Taylor’s forces invaded the capital, an African peacekeeping force bombed the plantation.

It’s an ugly chapter for a company that, for much of its history in Liberia, has been an unquestionable force for good and a rare source of economic livelihoods. Frontline and ProPublica’s investigation does a fine job exploring the perils that come with doing business in a conflict zone, and in countries that few other corporations take chances on. It also leaves one with some uncomfortable revelations about Firestone.

As Liberia’s current President Ellen Johnson Sirleaf told Frontline and ProPublica’s investigators in response to their findings about the company: “Sometimes we don’t even want to know.” Firestone remains her country’s largest corporate employer.