The Last Place God Made — Jack Higgins

Locals call it the Rio das Mortes—the treacherous Brazilian river where the Huna tribe is known to kill all who trespass. Despite the river’s deadly reputation, pilot Neil Mallory agrees to fly supplies to outposts there in hopes of making enough money to buy his passage back to England. But when he and fellow pilot Sam Hannah discover a field of massacred missionaries shot through with the Huna’s arrows, they decide to strike out along the River of Death to stage a daring rescue of the two nuns who are missing.

Their mission draws them deep into the treacherous jungle, where a final violent showdown with the Huna leads to a fateful decision that will change their lives forever.