He thought that they were lovers against the banker’s wish, and that the latter had himself committed the robbery in order to accuse this undesirable suitor of it and so get rid of him.

The search of the upper part of the premises completed, the party descended to the cashier’s office, where the superintendent remarked that their search had simply confirmed the opinions they had first formed.

The detective who was making a minute examination of the safe gave the most manifest signs of surprise, as if he had made a discovery of the utmost importance. The others at once gathered round and asked what he had discovered. After some hesitation he replied:

‘I have found out that the safe has been quite recently opened or shut in a hurry, and with some violence.’

‘How do you know that?’ the superintendent asked.

The detective, as he handed him the magnifying-glass, pointed out a slight chafing which had marked the varnish for a distance of twelve or fifteen centimetres.

‘Yes, I can see it,’ the superintendent said, ‘but what does it prove?’

‘Nothing at all,’ Fanferlot replied, though he did not think so.

This scratch seemed to him to confirm his theory, for the cashier could have taken millions without any need for haste. The banker, however, if he came downstairs quietly at night to rob his own safe, had a thousand reasons for haste and might easily have made the scratch with the key.

The detective, who had quite made up his mind to solve the mystery, was now more determined than ever to keep his theories to himself, as well as the interview he had witnessed.

‘In conclusion,’ he said to the superintendent, ‘I declare that the robbery was not committed by an outsider. The safe has not been forced, nor has any attempt been made to force it. It was opened by someone who knew the word and had the key.’

This formal declaration convinced the superintendent, who at once said:

‘I shall be glad of a minute’s private talk with M. Fauvel.’

Prosper and the detective went into the next room, and the latter, in spite of his theories, was quite determined to keep his eye upon the cashier, who had taken a vacant chair.

The other clerks were burning to know the result of the inquiry and at last Cavaillon ventured to ask Prosper, who replied with a shrug of the shoulders:

‘It is not decided.’

His fellow clerks were surprised to see that he had lost all trace of emotion and had recovered his usual attitude, one of icy hauteur, which kept people at a distance and had made him many enemies.

After a few minutes Prosper took a sheet of paper and wrote a few lines upon it.

The detective seemed to suddenly awaken out of a deep sleep, and the thought came to him that now he would find out something positive.

After finishing his short letter, Prosper folded it up as small as possible and threw it to Cavaillon, saying, as he did so, one word only:

‘Gypsy!’

This was effected with such skill and sangfroid that even the detective was surprised.

Before taking action the superintendent, either out of deference or from the hope of obtaining more information from a private conversation, decided to warn the banker.

‘There can be no doubt, sir,’ he said as soon as they were alone, ‘that this young man has robbed you. I should be neglecting my duty if I did not arrest him; afterwards the magistrate will either confirm his arrest or set him at liberty.’

This statement appeared to touch the banker, for he murmured:

‘Poor Prosper!’

Seeing the superintendent’s astonishment at this, he added:

‘Till today I had the utmost faith in his probity and would have trusted him with my fortune. I almost went down upon my knees to get him to admit his fault and promised him pardon, but I could not touch him. I loved him and do so still, in spite of the humiliation I foresee!’

‘What humiliation?’ asked the superintendent.

‘I shall be questioned.’ M. Fauvel quickly resumed. ‘I shall be obliged to lay bare to a judge my exact business position and operations.’

‘Certainly, sir, you will be asked a few questions, but your well-known integrity—’

‘But he was honest also. Who would have been suspected this morning if I had been unable to find 300,000 francs at once?’

To a man with a heart, the thought, the possibility even of suspicion, is a cruel suffering. The superintendent could see that the banker was suffering.

‘Compose yourself, sir,’ he said; ‘in less than a week we shall have evidence enough to convict the criminal, whom we can now recall.’

Prosper received the news of his arrest with the utmost calm. His only remark was:

‘I swear that I am innocent!’

M. Fauvel, who seemed much more disturbed than his cashier, made one last effort:

‘There is still time,’ he said, ‘reflect—’

Prosper took no notice of him, but drew a key from his pocket and put it on the shelf, saying:

‘There is the key of your safe; I hope you will recognize before it is too late that I have not stolen anything from you. There are the books and papers my successor will need. I must tell you, also, that without reckoning the 350,000 francs you will find a deficit in my cash.’

At the word deficit his hearers became all the more certain of his guilt; even the detective became doubtful of his innocence. The explanation, however, which Prosper gave soon diminished the gravity and significance of this deficit.

‘My cash is 3,500 francs short,’ he said. ‘I have drawn 2,000 francs of my salary in advance, and advanced 1,500 francs to several of my colleagues. Today is the last day of the month, and tomorrow we receive our salaries.’

‘Were you authorized to do this?’ asked the superintendent.

‘No,’ he replied, ‘but in doing so I have merely followed the example of my predecessor, and I am sure M. Fauvel would not have refused me permission to oblige my colleagues.’

‘Quite right,’ was M. Fauvel’s comment on the cashier’s remarks.

This completed the superintendent’s inquiry, and announcing that he was about to depart, he ordered the cashier to follow him.

Even at this fatal order, Prosper did not lose his studied indifference. He took his hat and umbrella and said:

‘I am ready to accompany you, sir!’

The superintendent shut up his portfolio and saluted M. Fauvel, who watched them depart with tears in his eyes and murmured to himself:

‘Would that he had stolen twice as much and I could esteem him and keep him as before.’

Fanferlot, the man with the open ears, overheard the expression. He had remained behind looking for an imaginary umbrella, with the intention of obtaining possession of the note Prosper had written, which was now in Cavaillon’s pocket. He could easily have arrested the latter and taken it by force. But after reflection the detective decided that it would be better to watch Cavaillon, follow him and surprise him in the act of delivering it.

A few judicious inquiries as he was leaving informed the detective that there was only one entrance and exit to the premises of M. Fauvel, the main entrance in the Rue de Provence.

The detective on leaving the bank premises took up a position in a doorway opposite, which not only commanded a view of the entrance, but by standing on tiptoe he could see Cavaillon at his desk.

After a long wait, which he spent in considering the facts of the robbery, he saw Cavaillon get up and change his office coat. A minute afterwards he appeared at the door, and glanced to right and left before starting off in the direction of the Faubourg Montmartre.

‘He is suspicious,’ thought the detective, but it was simply a desire to take the shortest cut, so that he might be back as quickly as possible, which caused him to hesitate.

He walked so quickly that the detective had some difficulty in keeping pace with him, till he reached number 39, Rue Chaptal, where he entered.

Before he had gone more than a step or two along the corridor the detective tapped him on the shoulder.