The first headline-grabbing day of public testimony in the House impeachment inquiry set the stage for much more to come.

It also left some big questions to be answered — most importantly, who will actually show up to testify?

The public hearings resume Friday with a witness all but certain to appear: Marie Yovanovitch, who was ousted as U.S. Ambassador to Ukraine by President Trump after what she’s described as a “concerted campaign” against her. Yovanovitch is arguably as important to the inquiry as diplomat Bill Taylor, the star of Wednesday’s show.

In closed-door testimony last month, Yovanovitch told investigators that Trump’s personal lawyer Rudy Giuliani led that campaign, and that Gordon Sondland, U.S. ambassador to the European Union, told her she should publicly support the president’s actions regarding Ukraine, or lose her job.

Also Friday, one of the question marks: the impeachment panel has scheduled a closed-door session with David Holmes, political counselor at the U.S. embassy in Ukraine. It’s unclear whether he’ll appear.

“An official familiar with the matter said Holmes is the person Taylor referred to in his testimony on Wednesday when he said an aide had overheard a conversation between Sondland and Trump in July about Ukraine conducting investigations,” reports the Associated Press.

On Saturday, in another closed-door hearing, Mark Sandy of the Office of Management and Budget is scheduled for to deliver a deposition. He seems unlikely to respond, since Trump ordered his administration not to cooperate with the inquiry.

Public testimony will continue next week, with eight more witnesses due to testify. All previously testified behind closed doors.

Two of them are expected to appear on Tuesday, Nov. 19: U.S. Army Lt. Col. Alexander Vindman and Kurt Volker, a former U.S. special envoy to Ukraine.

Vindman, who is European affairs director at the National Security Council (NSC), told investigators last month that he “did not think it was proper” for Trump to press Ukraine for an investigation of Joe Biden.

In a closed-door appearance Oct. 3, Volker gave investigators text messages saying Trump was unlikely to meet with Ukraine President Zelensky unless Zelensky promised to launch a Biden investigation. Volker, reports the Washington Post, “was one of three witnesses added to the hearings at the request of the Republican committee members.”

Also on tap for Tuesday are Jennifer Williams, Vice President Mike Pence’s national security aide, and Timothy Morrison, former senior director for the NSC and another of the witnesses sought by Republicans on the inquiry panel.

On Wednesday, Nov. 20, the lineup includes Gordon Sondland, U.S. ambassador to the European Union; Laura Cooper, special assistant secretary of defense for Russia and Ukraine, and David Hale, under secretary of state for political affairs.

On Thursday, the sole scheduled witness is Fiona Hill, former NSC Russia adviser. In previous closed-door testimony she told investigators about then-national security adviser John Bolton’s unease with the Ukraine affair, and about Giuliani’s campaign of off-the-books diplomacy.

It’s an ambitious schedule, and could easily slip beyond Nov. 21.

But whenever public testimony is complete, members of the three House committees taking part in the inquiry — Intelligence, Foreign Affairs and Oversight and Reform — will submit a report to the Judiciary Committee.

“Judiciary is expected to hold its own hearings and, eventually, vote on articles of impeachment,” the AP says. That would be followed by a vote in the full House of Representatives.

If articles of impeachment are approved as seems likely, a trial in the Senate would be next, probably beginning in early 2020.