Dial M for Murder

"Dial M for Murder " stars Grace Kelly, Ray Milland (as her husband), and Robert Cummings.   Milland discovers Kelly has fallen in love with Cummings .   He blackmails an old ex-con school acquaintance into killing her during a fake burglary .   The killer is to wait inside the apartment until Milland makes a phone call to his wife, but things do not happen as planned.