If she had not had her back turned to the garden; if she had not left the gate open behind her, and if the wind in the bamboos had not then made a noisy rustling, she would have seen the visitor or heard his steps on the gravel path.

Or if she had not been so absorbed in her subject and her cigarette she might have noticed that Mrs Gildea had looked up quickly a minute before and given a mute signal to the intruder not to interrupt the conversation untowardly..