At 8 am on March 23 of 2024, Tigran Gambaryan woke up on a couch in Abuja, Nigeria, where he’d been dozing since the predawn call to prayer. The house around him, which often buzzed with the nearby sound of generators, was eerily quiet. In that silence, the harsh reality of Gambaryan’s situation flooded back into his mind the way it had every morning for nearly a month: That he and his colleague at the cryptocurrency firm Binance, Nadeem Anjarwalla, were being held hostage in a Nigerian governme...