Ichthyologist Tonya Tikhonova and the chief engineer of the fishery plant, Ryazanov, are heading to the fishing seiner "Squall" (Shkval). Tonya loves Ryazanov, and this love frightens her. Ryazanov is also the object of affection of Panna, the wife of Ermak, the captain of the seiner. "Squall" is on course for Krutaya Bay — promising a good catch. Ryazanov and Panna go to the bay to check the composition of the plankton.