An idyllic British river: misty dawns, dancing mayflies, lazy trout and fluffy chicks paddling under the watchful gaze of their parents. "My Halcyon River" is an intimate portrait of a secret world where otters hunt on the midnight current, mink lie in wait to ambush unwary victims and gleaming kingfishers pierce the water to spear their prey. These dramas, both mortal and touching are revealed through the eyes of a man who has loved the river since he was a boy, cameraman Charlie Hamilton-James.