''Only the River Knows'' is a fly fishing film shot in New Zealand, Australia, Norway and Sweden. Back in 1988, one of the most iconic fly fishers of our time, Lars Lenth, spent three months exploring the fabled Lethe River and fishing for its abnormally large trout. 25 years later, Rolf Nylinder looses his was in the wilderness near Lethe. By chance, he finds the long-lost journal of Lars Lenth...