A riverboat captain named Wallins plays his flute as his tugboat moves down the river, carrying a load of pig irons. He often mistreats his African-American crew and is known to have killed three for various infractions. As they sail, another flute plays over Wallins’, and he flies into a rage at the perceived slight to his own music. The man playing is named Gallup, and he lives on a shantyboat. In anger, Wallins steers his tugboat into the shantyboat and destroys it, leaving Gallup to drown. His first mate jumps in to rescue him and pulls him on board, where Wallins demands that the other man confess that the captain is the better flute player. Gallup refuses and swears revenge on him, which leads the captain to attack him and then force him to move the pig irons until he gives in.  Later that night, Wallins takes out his flute to play when again he hears a flute from where Gallup is imprisoned. Again enraged, he takes the man’s flute and forces him to work for a day straight. However, Wallins’ deck boss takes matters into his own hands and forces Gallup overboard to drown, and the captain decides to save him so he can dole out justice on his own terms. Surprised that the captain would spare his life, Gallup offers him a deal: a musical competition in which the crew votes for the better player, and whoever loses must acquiesce and tell the other they are more gifted. Wallins agrees, and the two play for the crew. Upon the first verbal vote, Wallins wins, but after a secret ballot Gallup takes every vote. Wallins tries to back out on the deal, and Gallup dives overboard and swims to shore, where he lies in wait for his revenge. Later, he sees the tugboat returning up the river, blind because there is no light from the lighthouse that he usually mans. The boat crashes into shore, and while the crew frantically tries to save it, Gallup sneaks on board. He jumps Wallins and ties him to the ship, saying that unless the man follows through on their deal and admits his superior flute-playing, he will cut the ship loose and let him die with it. Wallins refuses, but asks for a final chance to play his flute. To Gallup’s surprise, he plays the tune that he originally did on the river. The shantyman respects him for his bravery and cuts him loose, and together they escape the ship. Wallins finally admits Gallup is the better player, but Gallup argues that he must be equally as good, and the two decide to play a duet.