The Bishop's Secret by Fergus Hume

Like that famous banquet, when Macbeth entertained unawares the ghost of gracious Duncan, the bishop's reception broke up in the most admired disorder. It was not Dr Pendle's wish that the entertainment should be cut short on his account, but the rumour -- magnified greatly -- of his sudden illness so dispirited his guests that they made haste to depart; and within an hour the palace was emptied of all save its usual inhabitants. Dr Graham in attendance on the bishop was the only stranger who remained, for Lucy sent away even Sir Harry, although he begged hard to stay in the hope of making himself useful. And the most unpleasant part of the whole incident was, that no one seemed to know the reason of Bishop Pendle's unexpected indisposition.

'He was quite well when I saw him last,' repeated poor Mrs Pendle over and over again. 'And I never knew him to be ill before. What does it all mean?'