An engineer for the Northern Power Company, Owen Merrill, arrives at the Muskalala River to make surveys for a dam site. For fifty years the river has been the exclusive fishing preserve of the Muskalala Salmon Club, now operated by Heather McHale. When his reason for being there is discovered, she detains him at the club while she sends out a distress call to the club's powerful members to meet at the lodge and take action to prevent the dam from being built. Already in love with his hostess/captor, Owen leaves for the dam site only to discover from his assistant, Steve Crowder, that she has gone into action to stop the project. He rushes to the Forest Commissioner's office and discovers she is already there. He tricks her into a telephone booth, and after locking her in gets the commissioner to sign a permit approving the dam. Unknown to Heather, her guides wreck a truck and take shots at the power-company workers. She stops that but, in her capacity as a Game Warden, arrests Owen for cutting trees too close to the river. She has him locked into the lodge storeroom and goes to see the commissioner. Owen, after discovering her guides have cut the supports on a new bridge, escapes and saves her life by stopping her car when she returns to the lodge. Taylor shows her the company intends to build "fish-ladders" that will enable the salmon to keep spawning and stay in the river, and everybody concerned is now happy.