For much of the two weeks leading up to his public appearance on Capitol Hill, Michael Cohen sat in his Park Avenue apartment, a legal pad and pen in his hands, as he tried to formulate his opening statement. In the background, he would occasionally hear his name on the television, repeated with increasing frequency as the day of his public reckoning drew nearer. Eventually, he settled on something close to the scathing rebuke of former boss Donald Trump that he delivered Wednesday morning before the House Oversight Committee. The president, he would say, is a crook, a cheat, a liar, and a racist who orchestrated a hush-money scheme in the run-up to the presidential election, inflated his wealth, and had advance knowledge of a WikiLeaks plot to release damaging e-mails about Hillary Clinton.

Cohen passed what he figured would be his final draft to his legal team. It was eviscerating, they thought. It struck the right tone, and presented a damning, first-person perspective on Cohen’s 10 years in Trump’s employ. But, his lawyers cautioned, Republicans on the committee would be looking for any opportunity to poke holes in his story. Cohen had already pleaded guilty to nearly a dozen criminal counts, including campaign-finance violations, financial crimes, and—perhaps most important—lying to Congress. They would relentlessly attack his credibility and discount his personal anecdotes without documentary evidence of Trump’s alleged misdeeds.

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It was around this point that Cohen saw a congressman on cable news discussing Trump’s financials, and he remembered that he had some of those documents. Federal agents had seized them from his former office in Rockefeller Center last April as part of a criminal investigation by the Southern District of New York. The boxes they’d returned were in a storage unit in the basement of his Trump-owned building—incidentally, the same building where Ivanka Trump and Jared Kushner keep an apartment. So he went down to look.

About nine boxes were there waiting for him. The first contained a bunch of junk. The second did, too. “Oh my god,” he said when he opened the third. He’d hit the mother lode. In the third box were three years of Trump’s financial statements, from 2011 through 2013, which Cohen pointed to on Wednesday as evidence that the president had purposefully inflated and deflated his personal assets when it suited him—to secure bank loans or land a higher spot on the Forbes 400 list, for instance, or to lower his tax liability. There were also countless personal notes from Trump, scrawled across newspaper clippings, printed articles, and torn-out pages from glossy magazines. One note, written in Sharpie across an unflattering article, urged Cohen to call a reporter and threaten him with a lawsuit; another, on a story prominently featuring Cohen, read simply, “Michael, enjoy this while it lasts.”

Other documents were potentially more damaging. The box also contained an e-mail with Trump Organization C.F.O. Allen Weisselberg, whose name came up almost as often as Trump’s in the House hearing on Wednesday. The exchange had to do with how Cohen would be reimbursed for the $130,000 payment he made to adult-film actress Stormy Daniels, 11 days before the election, in order to keep her from going public with allegations of an affair with Trump. In his testimony before the Oversight Committee, Cohen alleged that Trump and Weisselberg had direct knowledge of the negotiations leading up to the payment, and, according to Cohen, a plan to reimburse him in 11 installments. He told the committee that upon visiting Trump in the Oval Office in early 2017, the president brought up the reimbursements. The checks were on their way, Trump said, but had been delayed because it takes time for his personal correspondence to make its way through the White House mailroom.