Structure is how the writer chooses to order the events of the story. Does it follow a traditional structure with a beginning, middle and end, or does it follow a different order?
An Inspector Calls is written in three acts. Priestley cleverly structures the acts so that they end on gripping cliff-hangers. There is also a final climax and then a twist at the very end. This use of structure helps to keep the audience gripped and on the edge of their seats.
As we know, the Inspector is here to investigate the death of Eva Smith. What the audience don't know is what happened in the two years prior to the evening the play takes place. Priestley slowly reveals these events. We never actually meet Eva Smith but we empathise with her as a character. It is through the Inspector that we get a sense of who she is and what happened to her.
In the following extract, the Inspector begins his investigation and reveals why he is at the Birlings'.
Inspector: I'd like some information, if you don't mind, Mr Birling. (1)Two hours ago a young woman died in the infirmary. She'd been taken there this afternoon because she'd swallowed a lot of strong disinfectant. (2) Burnt her inside out, of course.
Eric: (involuntarily) My god!
Inspector: Yes, (3) she was in great agony. They did everything they could for her at the infirmary, but she died. Suicide, of course.
Even though this event happened off stage, the Inspector's use of language helps the audience imagine Eva's horrific death.
Consider how the ending of Act One adds to the drama of the play.
Sheila: (1) (laughs rather hysterically) Why - you fool - he knows. Of course he knows. And I hate to think how much he knows that we don't know yet. You'll see. You'll see.
(She looks at him almost in triumph.)
(He looks crushed. (2) The door slowly opens and the INSPECTOR appears, looking steadily and searchingly at them.)
Inspector: (3) Well?
Birling: That was the police. A girl has just died - on her way to the Infirmary - after swallowing some disinfectant. And a police inspector is on his way here - to ask some - questions.
[As they stare guiltily and dumbfounded, the curtain falls]
This is a very effective ending. The Birlings and Gerald are stunned, especially Mr and Mrs Birling and Gerald who just a minute ago had been sure they were in the clear. The audience would be shocked and left with lots of unanswered questions.
The ending also reflects Priestley's interest in theories about time, including the idea that individuals re-enter their lives again after death, living it all over again. They can make changes to their previous actions, beginning a new cycle where they do not repeat the mistakes of their past. We can see this in the structure of the play as the cycle of events is about to start all over again, with an investigation into the suicide of a young girl. Sheila and Eric have learned from their mistakes and could escape this cycle, whereas the others have not.