Like all the greatest plays in history, Sophocles’ Oedipus is a masterpiece because on every encounter it offers us something new. Sigmund Freud’s interpretation of the play — about the man who kills his father and marries his mother — needs no rehearsal. When I re-read the play recently, I was drawn to a quite different aspect of the drama: its status as the first great piece of crime fiction, a detective story in which, the investigator and perpetrator are revealed as the same person.

Every question Oedipus asks — how can we stop the plague that harrows Thebes? Who was the killer of Laius? What happened to Jocasta’s baby? — is eventually answered with the same word: Oedipus. The story works because of its watertight construction and formal beauty. Scene by scene, it entangles its protagonist a little more chokingly and, through the dreadful force of its own internal logic, brings down Oedipus inevitably as a spider might trap a fly.

Frank McGuinness, who has adapted Oedipus the King for Jonathan Kent’s production at the National Theatre in London, has also spoken about his relationship with the play. What springs most grippingly out of the drama for him is the tragedy of a son who loses his father, and of a father who loses his children. There can be few more devastating and yet unsentimental moments in theatre as when Oedipus, self-blinded and about to be driven from his home as a polluted exile, bids farewell to his children, by now revealed as the product of an incestuous marriage.

But more powerfully, and more profoundly, Kent’s production show what it looks and feels like when a person’s life unravels. The play ends with the line: “Call no man fortunate until he is dead.” In other words, you cannot judge a life to have been happy until it has ended. Sophocles warns us that fortunes can change in a day; that however prosperous and safe you are, it could all end tomorrow; that no one is safe from disaster. This is the deadly, timely message of the play. “Human happiness never remains long in the same place,” wrote Sophocles’s contemporary, the historian Herodotus. The comfort, cold as it is, is that Oedipus lives. He goes on, he takes his stick, and he walks away from Thebes — a wiser man.