Harold Pinter's first play for radio, and essential listening for anyone interested in the medium. It demonstrates with breathtaking simplicity the subjective landscape that audio drama can develop. There are three characters – Flora, her husband Edward, and a mute matchseller. We do not hear the matchseller speak or make any sound. Over the course of the play, Edward and Flora each project their own realities onto this mysterious figure – listen how one's own colorations of him morph with theirs.
The play is analyzed in greater detail in Elissa Guralnick's fabulous book, Sight Unseen, and I highly recommend listening to the play before reading her chapter devoted to it. The version below is the 2000 remake, starring Pinter and Jill Johnson. The original 1959 production starred Maurice Denham and Vivien Merchant, and I'm not sure it still exists. In any case, I've never heard it.