A police detective (Lee J. Cobb) covers things up when his lover (Jane Wyatt) kills her husband, but is then assigned to the case with his new partner: his own little brother (John Dall). 1950. Part 1 of 2.
Original movie from Internet Archive
Movie info from IMDB
Review @Some Came Running (slight spoiler alert)
Lee J. Cobb @Wikipedia
Jane Wyatt @Turner Classic Movies
Julie Cobb @Wikipedia