‘Then I may assume that you set out on your rounds at a quarter-past ten, a quarter-past eleven, a quarter-past—’
‘No, sir, it is an hour after finishing each round. I start the second round at a quarter-past eleven, and have it done by half-past eleven. I set out on the third at half-past twelve, and so on, sir.’
‘You are an ex-soldier, Mann—what branch?’
‘Finished as a sergeant, sir. I was an old regular, discharged unfit 1924.’
‘A man of method apparently, anyway,’ said Devenish. ‘Now, did you see or hear anything suspicious last night in the Store?’
He took out his note-book as he spoke.
‘Nothing at all, sir.’
‘No noise like a lift going up or down, no sound that might suggest an aeroplane engine?’
‘I didn’t hear any lift, sir, but then they are uncommon quiet. I did hear a faint sound like an engine up above, but I often hear that weekends, so I don’t count it suspicious.’
‘The dynamos in the basement were running? Why don’t these people take current from the mains?’
‘I don’t know anything about it, sir. I do know Mr Mander used to tinker with machines up above. I thought he was at it again last night; though it didn’t last long.’
Devenish nodded. ‘Let me see where this box of yours is, Mann,’ he said, and called softly to the detective at work in the lift, ‘I say, Corbett, run that lift up and down a bit for the next three minutes, will you, while I am away.’
Receiving an assent from his subordinate, he accompanied the watchman along the corridor, and down another at right angles, which ended in a sort of cabinet. This cabinet contained a seat, a switchboard and telephone, and the bell of a burglar-alarm. Devenish seated himself in the chair, and looked down the corridor. ‘You don’t see much of the Store from here,’ he remarked thoughtfully; ‘only a corner of it.’
‘So I’m not seen, either,’ replied his companion. ‘If I put on my torch, I might frighten any thieves, and if I keep the place dark I can’t see. But, dark or light, I can hear better than anyone else.’
Devenish smiled dryly. ‘You must have very acute hearing indeed, if you can hear slight sounds in a place as big as this, with partitions to cut sounds off or blur them.’
‘It isn’t that my ears are specially good, but this ear here, sir,’ said the man, with a quiet smile, and pointed to a tiny horn, like a gramophone-horn, at the level of his head, which projected slightly from the wall of the cabinet. ‘Mr Mander was great for the latest dodges. I just switch on this microphone here, and every sound comes my way. More than that, sir. There’s a kind of selective attachment to it, and it tells me from what quarter the sound comes, so I can take action.’
‘Royal Engineer?’ asked the detective gently.
‘Signals, sir. But you see what I mean.’
‘Turn on the switch now.’
Mann obeyed, then looked puzzled. The detective did not look so puzzled, but faintly startled.
‘Someone’s been monkeying with your buzz-saw,’ he murmured. ‘I don’t hear any of the noises magnified now.’
Mann had obviously some mechanical knowledge. He examined the horn and the switch, then looked at the electrical connections, and swore.
‘Cut a lead here, sir,’ he said.
Devenish took out his magnifier, and examined the thing closely, then he dusted the panelling in the region of the lead, and scanned it for finger-prints. None showed. Someone had interfered with the microphone, but he had left no traces while doing it.’
‘He must have been here while you went on one of your rounds. Did you not notice that there were no sounds coming through as loud as you would expect to hear them?’
‘I didn’t, sir, but you know how it is. I didn’t suspect anyone was here, and you aren’t so sharp after nothing has happened for two months on end.’
‘An unfortunate but truly human failing,’ agreed Devenish, ‘but I must admit to defects myself. For example, I have not been listening for the sound of the lift going up and down. I must get my man to keep it working.’
He went away, to return again in a minute, and raise a hand to command silence. It may have been the noises from the Store, but he could hear nothing of the moving of the lift, and realised that the experiment could not be made until the place was empty and perfectly quiet.
Explaining this to the watchman, he went off, and found himself in a couple of minutes in the shop window with the blind down, talking to his superintendent, who had just arrived from the Yard, and the surgeon, who sat smoking a cigarette, and watching the last efforts of the lower ranks, as they measured and surveyed and plotted the big space. When he had finished explaining what he had done, Devenish was rewarded by a nod of approval from the superintendent.
‘Any sign of the bullet yet, sir?’ he asked.
‘None at all,’ said the big man stolidly. ‘High-velocity bullet, Dr Grindley thinks.’
‘Knows,’ said the surgeon, puffing. ‘I saw enough of them during the war. Steel-jacketed, I should say.’
‘Not that Mauser?’ asked Devenish gently.
‘I ought to have been a gunner,’ said the surgeon, smiling. ‘I know all about ’em—all kinds. That Mauser is new, been fired once. But I think your experts will agree that it was fired with blank. I won’t swear, but that is my opinion.’
‘Possible,’ murmured Devenish. ‘A man who would take the trouble to set up his victims as specimens in the window here wouldn’t leave the gun on view.’
‘Was the shot fired at close quarters?’ said the superintendent.
‘I should say not. Not very close anyway.’
‘How long should you say he had been dead?’
The surgeon reflected. ‘It isn’t so easy to answer that as some people imagine. I should say roughly between twelve to fourteen hours, but I may be sadly out.’
‘And the young woman?’
‘Less, I should say, but I can’t tell you how much less. In neither case does the bleeding seem to have been extensive—a sporting bullet with a more or less soft nose would have been different. The other wound was made by a weapon that did not—’
‘Wait a moment,’ said Devenish. ‘If she was killed after him—’
‘Then he didn’t do it,’ said the surgeon. ‘I admit that! I don’t think either of them did it to each other!’
Devenish smiled faintly. ‘Well, you’ll have the P.M., and then we shall know more. I thought, superintendent, of going to see the man in charge of the aeroplane department. I see you have cleared most of the people out of the Store, but the executives will be here.’
‘I asked them to stay in Mr Mander’s private office,’ said the other. ‘I am going to have a talk to them. But if you care to see one alone—’
‘If he would come to me in his department above, sir,’ said the inspector, ‘I will go there now.’
The superintendent nodded. ‘Very well. I’ll send him.’
The inspector nodded to the surgeon, and went away. Taking one of the automatic lifts, which had upon a board outside ‘To Sporting and Aeroplane Departments’, he found himself on the first floor, and presently arrived in an immense room looking over a street at the side of the Stores building. Housed in this department (some ready for flight, and some in the various stages of folding that made the Mander Hopper such a boon to the private