Farlig vår (1949)

A young prostitute, Gullan Svan, is murdered one night. The police suspects that the murderer is a student, since she had a lot of students as customers. The murderer stole a picture of Gullan after he killed her, a picture which later is found in a rented tuxedo when the tuxedo is returned. Four students decide to solve the case, but it seems that the truth is even closer than they first suspected...