Tanja Bulkova arrives in Finland under the name Toini Salonen and, with the help of spy chief Rosenberg, becomes the secretary of engineer Rautavuori and discovers the drawings of a secret invention.
The old man at the Eirtola house warns the new maid Eriikka about the fate of Jenny, the summer girl. Jouko, a university student from Eirtola, arrives home for the summer and begins to court the pretty maid. At the cattle shed, Eriikka finds a box, the contents of which she examines together with Pastor Tuomo Ahomaa. The tragic fate of Jenny, the summer girl, is revealed.
A man mixed up in suspicious activity is murdered in the studio of photographer Ilmari Lavio. At the same time a charming woman has entered the studio, but Lavio does not want to report her to the police. The photographer begins to follow the beauty who calls herself Soile Mäntymaa and through her traces a league of spies.
