‘You could have seen it if you’d asked for it. There just wasn’t anything to it. We’d established that the case belonged to Stephen Herriard; the experts didn’t find any finger-prints on it; and that’s all there was to it.’

‘I should have known better than to have taken anyone’s word for it!’ said Hemingway in bitter accents. ‘Didn’t it strike you that it was highly unusual, not to say suspicious, that there weren’t any finger-prints on the case?’

‘I suppose,’ said Colwall, whose brain moved slowly, ‘it must have been wiped.’

‘Yes,’ retorted Hemingway. ‘That’s just what I suppose, too! And if you think young Herriard dropped it, all accidental-like, first taking the precaution of wiping his finger-prints off it, all I can say is that you’ve got a nice, unsuspicious nature, Inspector!’

Colwall bridled a little at this, but as the inference of Hemingway’s words sank into his mind, he flushed, and said: ‘Of course, it’s your business to spot things like that. I don’t deny that what with one thing and another it just didn’t occur to me that it was funny, not finding any prints on the case. Couldn’t have got wiped off in young Herriard’s pocket, could they?’

‘No,’ Hemingway said positively. ‘They might have got a bit blurred, but you’d be bound to find some trace. Ever cleaned a bit of silver, and tried to get your own finger-prints off it? It takes some elbow-grease, I give you my word.’

‘That’s right, it does,’ nodded Colwall. ‘Same with brasswork. But this was a gold case. One of those large, flat ones, with a monogram on it.’

‘I ought to have had a look at it in the first place,’ Hemingway said, annoyed with himself. ‘Come on! Let’s go and have a talk with your expert!’

But no expert was needed to convince him that the cigarette-case had been wiped clean of all betraying marks. It was still held in the crutch in which it had been placed upon discovery, and its smooth golden surface showed no smudge or blemish.

‘Might just have come out of the shop,’ grunted Colwall. ‘Looks like new, barring a few scratches. Well, none of my men destroyed any prints, that I will answer for!’

‘I don’t suppose they did. This case has been carefully polished.’

‘Well, that has torn it!’ Colwall said. ‘Do you figure it was planted in the room to throw suspicion on young Herriard?’

‘That’s about the size of it,’ said Hemingway. ‘One thing’s certain: he didn’t leave it there himself.’

‘Then it pretty well clears him,’ said Colwall regretfully. ‘I must say, I thought all along it was him. A bit disheartening, isn’t it?’

‘I wouldn’t say that,’ replied Hemingway, who seemed to have recovered his cheerfulness. ‘In fact, I regard it as a highly promising development.’

‘I don’t see how you make that out,’ said Colwall, staring at him.

‘I was beginning to think that this was going to be the one case where the guilty party didn’t once slip up. Well, he did slip up,’ said Hemingway, pointing an accusing finger at the cigarette-case. ‘Just like a lot of others before him, trying to be too clever. The way I see it, planting this case was an unrehearsed effect. If he’d thought of it when he worked out the rest of his details, I daresay he’d have arranged for us to have found Stephen’s finger-prints on the case. We can take it that Miss Dean’s testimony was correct: she put the case down on the table at her elbow. Our unknown friend saw it there, and thought it would make a nice piece of evidence against Stephen. He picked it up, and probably slipped it into his pocket, either forgetting not to touch it with his bare hand, or not having the time to handle it through his handkerchief. But when it came to planting it, he wasn’t the man to forget that he mustn’t leave any prints on it, so he polished it good and hard. Well, it’s restored my belief in the fundamental stupidity of murderers. They all slip up sooner or later, though I admit this one’s sharper than most.’