Nightkill

A woman's lover poisons her cruel husband, a rich businessman, in front of her. She becomes more terrified when she finds the lover dead as well. A police detective suddenly shows up at her door.

Nightkill is a 1982 mystery crime movie directed by Ted Post, starring Robert Mitchum, Jaclyn Smith, James Franciscus. It holds an IMDb rating of 5.5/10 from 1,026 votes and runs 1h 37m.