The Bride Wore Black (1968)

After newly widowed Julie Kohler's (Jeanne Moreau) mother stops her from commiting suicide, she hatches a different plan to deal with her grief. In a small black book, she lists five men. One by one she visits the men with murderous intentions, assuming different identities to get close to them. Only one man remains elusive, having been captured by the cops before Julie could reach him -- but despite the obstacles, Julie intends to see her task through to the end.