A Night for Crime
(1943)

Investigative reporter Susan Cooper and her boyfriend, Joe Powell, here a suspicious noise from the apartment next door, and rush in. They find her neighbor Mona Harrison, dead.  Mona is an actress, in the middle of filming a blockbuster that was expected to launch her career.  Strangely, new sightings and photographs of the dead Mona show up.  And, the studio head seems to think he will still be able to finish filming the picture.

Mona had an identical twin sister, that no one knew about.  The twin sister's boyfriend, Arthur Evans, got a job as Mona's driver.  The twin sister and driver killed Mona.  They intended to dispose of the body, and have the twin take Mona's place and take over her career.  However, Susan and Joe rushing in and finding the body ruined that plan.   Arthur Evans tries to run Susan's car off the road, but ends up killing himself instead.  When the twin sister is confronted, she tries to escape, but falls to her death from the hotel window.  Joe proposes marriage to Susan (that kind of comes out of nowhere, but in 1940s Hollywood, a happy ending had to include her getting married.) 

Thanks Joseph C!