Earthbound

Nick and Ellen's second honeymoon in Switzerland is interrupted when he is called back to Paris on business. But it turns out to be funny-business when he discovers his ex-mistress Linda sent him the telegram. Nick spurns her, leading her to shoot and kill him. His ghost cannot rest, though, since Linda's husband Jeff is arrested for the crime and tried. Nick hovers over Ellen guiding her to the evidence that will clear Jeff and convict Linda, at which point he can rest at peace (imdb)