The headache started in the morning. It was a Thursday last June, and Jeff Zucker, president of CNN Worldwide, was working on the final preparations for New Day, the morning show he was set to debut four days later. From the moment Zucker took over CNN in January 2013, he had been focused on getting the morning right. He was a morning-television savant, after all, having led the Today show on a storied run of ratings dominance. And CNN’s early show, Starting Point With Soledad O’Brien, had become a symbol of the network’s slide from cable-news pioneer to industry laggard. O’Brien drew just 260,000 viewers, compared with more than a million people who watched Fox & Friends and some 450,000 viewers of Morning Joe on MSNBC.

Zucker had built the new morning show around Chris Cuomo, a brash 42-year-old hire from ABC News and the younger brother of the governor. But finding a female co-anchor had been difficult. His first choice, CNN host Erin Burnett, balked. Zucker ultimately settled on Kate Bolduan, a 29-year-old Washington, D.C., correspondent. In meetings, Zucker gushed about Cuomo and Bolduan’s chemistry, speaking as if he had found a cable analog to Katie Couric and Matt Lauer. “I’ve never seen anyone test so well,” Zucker said.

But that morning, as he led the 9 a.m. editorial meeting, he felt as if his head were about to explode. It wasn’t because he didn’t like the updates he was getting from producers. He felt like his brain was in a vise. Afterward, at a luncheon honoring former Time Warner CEO Richard Parsons, he had the misfortune of being seated in front of a New Orleans jazz ensemble, a tuba blaring in his ear. The pounding grew worse, so he went home and climbed into bed. “I never leave work,” he told me recently in his office off CNN’s Columbus Circle newsroom. It wasn’t any better the next morning, and he called in sick. When he woke up Saturday, the left side of his face was completely numb, his left eye swollen shut, his speech slurred. “I thought I’d had a stroke,” he said.

He rushed to the emergency room at New York Presbyterian. The doctor told Zucker that it wasn’t a stroke. He had Bell’s palsy, a rare disease that attacks the seventh cranial nerve, leading to facial paralysis. While doctors don’t know what causes it, they believe high levels of stress — say, launching a flagship morning show — might be a trigger. The symptoms, the doctor said, would likely subside in a few weeks. “I’ve dealt with a lot of shit in my life; two-to-four weeks I could deal with,” Zucker told me.

He decided to return to CNN at 6 a.m. on Monday for New Day’s debut. He couldn’t afford to be out at such a crucial moment. New Day was important for CNN, yes, but also for Zucker’s legacy. He wanted to prove he could recapture his Today show success — not for his critics but for himself.

When he arrived that morning, producers were shocked by his appearance. “I’m not in pain. I know it’s a distraction. Let’s move on,” he told them. But he wouldn’t find any relief from his stress that morning. New Day’s debut ratings were actually worse than Soledad O’Brien’s show’s. That afternoon, he got more bad news: A neurologist told Zucker it might take three months for his face to fully heal. Even that turned out to be optimistic. “I haven’t been able to smile in 14 months,” he told me.

In broadcast television, few have experienced higher highs, and lower lows, than Jeff Zucker. He was just 26 when he started as executive producer of Today in 1992, and he quickly turned the show into a ratings machine. By the time he was 40, Zucker was the CEO of NBC Universal. It was the fastest ascent up the executive ranks in television history. But what people remember most about his reign as CEO is not the company’s profits — fueled by thriving cable networks, a film studio, and theme parks—but the collapse of NBC’s prime-time lineup and the messy public war between Jay Leno and Conan O’Brien. In 2010, when Comcast acquired NBC, Zucker was forced out. He reunited with Couric to launch her syndicated daytime show at ABC, but the experiment flopped, and according to three sources, ABC was preparing to dump Zucker shortly after the show went on the air in September 2012. It’s not easy being a media mogul.

It was around this time that Jim Walton, the longtime president of CNN Worldwide, resigned under pressure. Zucker had been interested in CNN for years, but by this point the cable network was in bad shape — partly thanks to Zucker himself. As head of NBC Universal, he had pushed MSNBC to fashion a liberal response to Roger Ailes’s right-wing megaphone at Fox. The two loud voices at the poles left CNN’s low-decibel newscasts drowned out in the middle. Its viewership had fallen to its lowest levels since 1991. Though CNN’s website is a power¬house, with more than double the traffic of the New York Times’, and the network remains profitable — to the tune of $600 million this year, largely derived from long-term subscription contracts with cable providers — the ratings were an embarrassment, especially in prime time. CNN executives discussed the disappearing audience in existential terms. How do you succeed as a straight news channel when people don’t get their news from their televisions anymore? Was it possible for anyone to return CNN to No. 1?