The Ukrainian-born stepson of a prominent Deutsche Bank exec who took his own life has been cooperating with the FBI and Congress to expose President Donald Trump’s ties to the bank. New York Times journalist David Enrich tells the troubled story of Val Broeksmit, the 43-year-old adopted son of William Broeksmit, in an excerpt from his upcoming book, Dark Towers. In it, he describes how Broeksmit discovered his father’s bank files after he hanged himself in 2014, and found “detailed information about what was going on deep inside the bank.” Enrich says there were minutes of board meetings, financial plans, spreadsheets and “evidence of his father’s misery.”

Broeksmit took those files to the FBI in February and has been helping the bureau sort through what they mean with an eye to exposing how they might tie Trump to dirty Russian money and potentially even tax crimes. Enrich reports Broeksmit, an out-of-work musician with chemical-dependency issues, tried extracting money from the FBI in exchange for cooperation, but finally settled on an advisory title. “The man whom everyone had discounted and demeaned had managed to get his information into the hands of the Federal Reserve, Congress and the FBI.” Enrich writes. “Even if the documents ultimately prove underwhelming to these powerful investigators, Mr. Broeksmit had accomplished one of his life’s goals: He mattered.”