This time he won't be alone: Derek Holtzer, a government psychologist, will accompany him to observe and take notes. But during a freak storm, Derek is hit by lightning and falls into a coma. Their radio transmitter is dead. Brian is afraid that Derek will die of dehydration unless he can get him to a doctor. His only hope is to build a raft and try to transport Derek a hundred miles down the river to a trading post -- if the map he has is accurate.