Web of Fear (1964)

Constance Brunel ,a forty-something widow ,involuntary witnesses a murder: following a quarrel, Hugo ,a handsome young man ,strangles his lover,Pascale.The criminal takes refuge in Constance's apartment.She falls in love with him.Shortly after, she receives anonymous letters to squeeze money out of her.Soon,she discovers she has been framed :Hugo 's mistress is not dead .Constance's revenge will be ruthless.