Complex sentence: Nathan had found out about the gold, but was incarcerated before he could steal it, and told Bannister about the gold while in prison in the hope of convincing the attorney to get him released, unwilling to accept that Bannister was unable to do so.
Split into simpler sentences: Nathan had found out about the gold, but was incarcerated before he could steal it. While in prison, he told Bannister about the gold in the hope of convincing the attorney to get him released, unwilling to accept that Bannister was unable to do so.