Kill the Fatted Calf and Roast It (1970)

Original title: Uccidete il vitello grasso e arrostitelo

After many years of living abroad, a troubled young man returns home due to the death of his father (who he suspects was actually murdered). He attempts to untangle that mystery while still carrying an unhealthy obsession toward his mother, who committed suicide ten years ago. This obsession then draws in his attractive cousin and takes a sexual turn.