‘Shortly before seven,’ replied Day.

‘Can you prove you were at the theater all evening?’ demanded Kelley.

‘Why, yes, I went with a friend.’

‘He’s been dead about six hours, Inspector,’ said the police surgeon, finishing his examination at this point. ‘A deep knife wound, below the heart.’

As Fordney picked up an earring from the floor, Day exclaimed: ‘Why, that belongs to his fiancée.’

‘Well, there’ll be no wedding bells for him,’ remarked Kelley, with a start as he discovered that Day’s cane was a sword-stick with a long, thin, shining blade.

‘Any blood, Inspector?’ asked Fordney.

‘None. Clean as a whistle.’

‘Well, Day, looks mighty bad for you,’ stated the Professor. ‘I don’t know yet whether you killed him with that cane, or whether you killed him at all, but I do know you were here a few minutes after he was stabbed.’

[How did the Professor know?]