Like Blow-Out

A man, stumbling home drunkenly late one night, passes by a doorway which he uses to prop himself up on momentarily. He hears static, and looks around for the source of the noise. It's an intercom device, but for some reason it's emitting the noises from inside the house. Through his alcoholic haze, he can make out two voices - planning the death of someone whom our hero finally realises is a friend of his.