 After a 450-mile journey inland, he uncovered a trail of people being handed over to settle debts or seized by Portuguese agents and taken in shackles to the coastal towns.Once there he was enraged to find that Portuguese officials "freed" them and changed their status to that of voluntary workers who agreed to go to São Tomé for five years.Despite ill health so severe that he feared he had been poisoned Nevinson followed the slaves' journey to São Tomé.