The House committee investigating the Jan. 6 attack on the Capitol plans to return to prime time on Thursday to deliver what amounts to a closing argument in the case it has made against former President Donald J. Trump, accusing the former commander in chief of dereliction of duty for failing to call off the assault carried out in his name.

To do so, the panel will put two military veterans — Representative Elaine Luria, Democrat of Virginia and Representative Adam Kinzinger, Republican of Illinois — front and center in leading its presentation and questioning.

Ms. Luria, the only Democrat on the panel involved in a competitive re-election race, served in the Navy for more than 20 years and achieved the rank of commander. Mr. Kinzinger is an Air Force veteran who flew missions in Iraq and Afghanistan. One of the witnesses they plan to question in person, Matthew Pottinger, who was deputy national security adviser under Mr. Trump and the highest-ranking White House official to resign on Jan. 6, 2021, is a Marine Corps veteran.

In an interview previewing the hearing, which is scheduled for 8 p.m. on July 21, Ms. Luria said the panel planned to document in great detail how Mr. Trump did nothing for more than three hours while his supporters stormed the Capitol, raising ethical, moral and legal questions around the former president.

“The captain of a ship cannot sit there and watch the ship burned to the waterline and not do anything to stop it,” Ms. Luria said, invoking her experience in the Navy, where she worked on nuclear reactors. “And that’s exactly what he did.”

Ms. Luria said the panel planned to elicit in-person accounts of what went on in the West Wing on Jan. 6 from Mr. Pottinger and Sarah Matthews, a former White House press aide who had resigned in the aftermath of the riot. It also plans to play recorded testimony from Pat A. Cipollone, the former White House counsel, and others to document Mr. Trump’s inaction on Jan. 6.

“We have accounts from people who observed him,” Ms. Luria said. “There was no concern, anger, distress. He wasn’t upset by it.”

The committee plans to demonstrate that Mr. Trump had the power to call off the mob but refused to do so until after 4 p.m. that day — and then only after hundreds of officers had responded to the Capitol to support the overrun Capitol Police force, and had begun to turn the tide against the mob, making it clear that the siege would fail, according to committee aides.

The panel also plans to show outtakes from Mr. Trump’s video remarks of Jan. 7 in which he struggled to condemn the violence and promise a peaceful transfer of power, according to a person familiar with the committee’s plans. The plans to show the outtakes were reported earlier by The Washington Post.

Representative Bennie Thompson, Democrat of Mississippi and the chairman of the committee, plans to preside over the hearing remotely, after having tested positive for Covid-19 this week.

The panel has already started detailing some of its evidence of Mr. Trump’s inaction. Ms. Matthews has told the committee that a tweet Mr. Trump sent attacking Vice President Mike Pence while the riot was underway was like “pouring gasoline on the fire.”

Mr. Trump had tried unsuccessfully to pressure Mr. Pence, who was inside the Capitol as rioters breached the building chanting “Hang Mike Pence,” to reject Congress’s official count of electoral votes to confirm Joseph R. Biden Jr. as the president-elect.

Both Mr. Pottinger and Ms. Matthews have cited that tweet as contributing to their desire to leave the White House.

“These were people who believed in the work of administration, yet, on this day, when faced with the circumstances, the president’s inaction, and some of the statements he made, they decided they were done, they were going to resign,” Mrs. Luria said. “That is very powerful when you heard from them directly.”

The committee has also said it received testimony from Keith Kellogg, a retired lieutenant general who was Mr. Pence’s national security adviser. He told the panel that Ivanka Trump, Mr. Trump’s eldest daughter, urged her father at least twice to call off the violence, as did Mark Meadows, the chief of staff, and Kayleigh McEnany, the White House press secretary.

The panel has also released text messages from Fox News hosts, including Sean Hannity and Laura Ingraham, and Donald Trump Jr., one of the president’s sons, calling for him to do more to stop the violence that day.

“Anyone who came into contact with him that day and everyone who had access to him, from what they’ve shared with the committee, made some degree of effort to try to get him to do more,” Ms. Luria said.

At each of its hearings this summer, the panel has presented evidence that lawmakers and aides believe could be used to bolster a criminal case against Mr. Trump. The committee has uncovered new details that they believe could provide evidence of a conspiracy to defraud the American people and Mr. Trump’s own donors; revelations about his plan to submit false slates of electors that could lead to charges of filing false documents to the government; and disclosures about his plot to disrupt the electoral count on Capitol Hill that suggest he could be prosecuted for obstructing an official proceeding of Congress.

While there are penalties for members of the military who are found derelict in their duties, Ms. Luria said she was not sure Mr. Trump could be charged with a criminal offense as a result of his inaction.

Even so, she said, Thursday’s hearing was expected to be a capstone in the a series of hearings throughout June and July in which the panel has laid out its initial findings from more than 1,000 interviews.

The panel is expected to continue its investigation, adding to its work in anticipation of the release of a preliminary report on September. The committee could also call more public hearings, members have said.