And the irony is that her dismissal comes just as she expected to vault into a much bigger one.

When I had lunch with Schulman, 53, last Thursday in New York City, she talked about moving from her current position at the drug giant—general counsel and head of its $3.2 billion global healthcare business—to head three units: vaccines, oncology and global healthcare. That trio of businesses would have given her responsibility for more than $8 billion in annual revenue.

Something went awry between Thursday–when Schulman was prepping for a celebratory dinner at Manhattan’s elegant Le Bernardin restaurant with her legal team—and 9 a.m. Tuesday, when Pfizer disclosed her departure in a tersely written press release that said her exit is by “mutual agreement.”

Did Schulman make a power play that turned out to be fatal? Did her reputation as a consummate self-promoter rub her boss the wrong way? Did she clash with one of her senior colleagues? Whatever the back story, it’s clear that Pfizer is losing a fast-rising executive who seemed in pursuit of the top job at the company.

As Schulman explained over our lunch, her career path was unconventional. In 2008, she left law firm DLA Piper, where she was a star litigator earning almost $6 million annually, to join Pfizer, where her initial pay was a sliver of that. More important than the money, though, was her belief that then-CEO Jeff Kindler, a former general counsel at McDonald’s (MCD), would give her broad responsibilities beyond legal.

It didn’t turn out that way. While Schulman and Kindler got along initially, their relationship soon soured. She played a role in his 2008 ouster, which Fortune detailed in an award-winning 2011 cover story.

Schulman found an advocate in Kindler’s successor, Ian Read, who is now Pfizer’s chief executive. Read put her in charge of Pfizer Nutrition, while she held onto her post as the company’s chief lawyer. A mother of three boys, Schulman juggled her jobs happily–wanting to stay on as general counsel, she admitted, in case she failed as an operator.

She did not fail at operations. She expanded the $2 billion-a-year nutrition business and improved its profitability. Pfizer sold the unit to Nestle (NSRGF) for a stunning $11.85 billion in 2012.

Eager to run a bigger business, Schulman got a plum assignment heading global healthcare, with well-known brands such as Advil, Chapstick and Centrum vitamins. Meanwhile, she ascended to be one of Pfizer’s top-paid executives. Her compensation, including options, totaled $5.6 million in 2012, according to Pfizer’s proxy.

Pfizer did not return Fortune‘s phone calls. Amidst Schulman’s sudden exit, her intended assignment goes to Albert Bourla, a 20-year Pfizer veteran. He will be group president of Vaccines, Oncology and Consumer Healthcare. Susan Silbermann, meanwhile, is Pfizer’s new president and general manager of Global Vaccines.

At a company famous for palace intrigue, there’s a deja vu in this latest drama. Speculation about who will someday replace Read as Pfizer’s CEO ensues. For now–until the next upheaval, at least–new division chiefs Bourla, Geno Germano, and John Young emerge as the top contenders.