The curtain rises on "[a] late evening in the future." It is Krapp’s 69th birthday and he hauls out his old tape recorder, reviews one of the earlier years – the recording he made when he was 39 – and makes a new recording commenting on the last 12 months.
Krapp is sitting in his den, lit by the white light above his desk. Black-and-white imagery continues throughout.
On his desk are a tape-recorder and a number of tins containing reels of recorded tape. He consults a ledger. The tape he is looking to review is the fifth tape in Box 3. He reads aloud from the ledger but it is obvious that words alone are not jogging his memory. He takes childish pleasure in saying the word‘spool’.
The tape dates from when he turned 39. His taped voice is strong and rather self-important.
The voice mentions that he’s just celebrated his birthday alone "at the wine house" jotting down notes in preparation for the recording session later. His bowel trouble is still a problem and one obviously exacerbated by eating too many bananas. "The new light above my table is a great improvement," reports the 39-year-old Krapp, before describing how much he enjoys leaving it, wandering off into the darkness, so that he can return to the zone of light which he identifies with his essential self. He notes how quiet the night is.
The voice reports that he has just reviewed an old tape from when he was in his late twenties. It amuses him to comment on his impressions of what he was like in his twenties and even the 69-year-old Krapp joins in the derisory laughter. The young man he was back then is described as idealistic, even unrealistic in his expectations. The 39-year-old Krapp looks back on the 20-odd-year-old Krapp with the same level of contempt as the 20-odd-year-old Krapp appears to have displayed for the young man he saw himself for in his late teens. Each can see clearly the fool he was but only time will reveal what kind of fool he has become.
The voice reviews his last year, when his mother died. He talks about sitting on a bench outside the nursing home waiting for the news that she had died. When the moment comes he is in the process of throwing a rubber ball to a dog. He ends up simply leaving the ball with the creature even though a part of him regrets not hanging onto it as some kind of memento. Krapp at 69 is more interested in his younger self's use of the rather archaic word "viduity" (Beckett had originally used "widowhood" in early drafts) than in the reaction of the voice on the tape to their mother's passing. He stops listening to look up the word in a large dictionary.
He returns to the tape. The voice starts to describe the revelation he experienced at the end of a pier. Krapp grows impatient and gets worked up when his younger self starts enthusing about this. He fast-forwards almost to the end of the tape to escape the onslaught of words. Suddenly the mood has changed and he finds himself in the middle of a description of a romantic liaison between himself and a woman in a punt. Krapp lets it play out and then rewinds the tape to hear the complete episode. Throughout it he remains transfixed and visibly relives the moment while it is retold.
Afterwards, Krapp carefully removes this tape, locates a fresh one, loads it, checks the back of an envelope where he has made notes earlier, discards them and starts. He is scathing when it comes to his assessment of his thirty-nine-year-old self and is glad to see the back of him. He finds he has nothing he wants to record for posterity, save the fact he "Revelled in the word spool ." But he does mention a trip to the park and attending Vespers, where he dozed off and fell off the pew. He also mentions his recent literary disappointments: "seventeen copies sold", presumably of his last book, eleven of which have gone not to interested readers but to foreign libraries; "Getting known," he sarcastically summarises. His sex life has been reduced to periodic visits by an old prostitute recalling the jibes made in Eh Joe : "That slut that comes on Saturday, you pay her, don't you? ... Penny a hoist tuppence as long as you like."
Unlike his younger selves, Krapp has nothing good to say about the man he has become and even the idea of making one "last effort" when it comes to his writing upsets him. He retreats into memories from his dim and distant past, gathering holly and walking the dog of a Sunday morning. He then remembers the girl on the punt, wrenches off the tape he has been recording, throws it away and replays the entire section again from the previous tape. It is a scene of masochism reminiscent of Croak in Words and Music , tormenting himself with an image of a woman’s face. This time he allows the tape to play out. It ends with the thirty-nine-year-old Krapp determinately not regretting the choices he has made, certain that what he would produce in the years to come would more than compensate him for any potential loss of happiness.
Krapp makes no response to this but allows the tape to play on until the final curtain. "Krapp’s spool of life is almost wound, and the silent tape is both the time it has left to run and the silence into which he must pass." Whereas the younger Krapp talks about the "fire in me" the tired old man who sits listening is simply "burning to be gone." The title of the play seems obvious, that what we have witnessed is the recording of Krapp’s final tape, "yet there is an ambiguity: 'last' can mean 'most recent' as well as 'ultimate'. The speaker in Browning's My Last Duchess is already planning to marry his next duchess ... Still, one hopes for Krapp's sake that he will be gone before another year is over."