One afternoon it seemed that he, at length, had his chance.  There entered a maidservant with a prescription to be made up and sent as soon as possible.  A glance at the name delighted Mr. Farmiloe; it was that of the richest family in the suburbs.  The medicine, to be sure, was only for a governess, but his existence was recognised, and the patronage of such people would do him good.  But for the never-sufficiently-to-be-condemned handwriting of Dr. Bunker, the prescription offered no difficulty.  Rubbing his palms together, and smiling as he seldom smiled, he told the domestic that the medicine should be delivered in less than half an hour.

Scarcely had he begun upon it, when a lady came in, a lady whom he knew well.  Her business was at the post-office side, and she looked a peremptory demand for his attention.  Inwardly furious, he crossed the shop.

‘Be so good as to tell me what this will cost by book-post.’

It seemed to be a pamphlet.  Giving a glance at one of the open ends, Mr. Farmiloe saw handwriting within, and his hostility to the woman found vent in a sharp remark.

‘There’s a written communication in this.  It will be letter rate.’

The lady eyed him with terrible scorn.

’You will oblige me by minding your own business.  Your remark is the merest impertinence.  That packet consists of MS., and will, therefore, go at book rate.  Be so good as to weigh it at once.’

Mr. Farmiloe lost all control of himself, and well-nigh screamed.

’No, madam, I will not weigh it.  And let me inform you, as you are so ignorant, that to weigh packets is not part of my duty.  I do it merely to oblige civil persons, and you, madam, are not one of them.’

The lady instantly turned and withdrew.

‘Damn the post-office!’ yelled Mr. Farmiloe, alone with his errand-boy, and shaking his fist in the air.  ’This very day I write to give it up.  I say—­damn the post-office.’

He returned to his dispensing, completed it, wrapped up the bottle in the customary manner, and despatched the boy to the house.

Five minutes later a thought flashed through his mind which put him in a cold sweat.  He happened to glance along the shelf from which he had taken the bottle containing the last ingredient of the mixture, and it struck him, with all the force of a horrible doubt, that he had made a mistake.  In the irate confusion of his thoughts, he had done the dispensing almost mechanically.  The bottle he ought to have taken down was that, but had he not actually poured from that other?  Of poisoning there was no fear, but, if indeed he had made a slip, the result would be a very extraordinary mixture; so surprising, in fact, that the patient would be sure to speak to Dr. Bunker about it.  Good heavens!  He felt sure he had made the mistake.

Any other man would have taken down the two bottles in question, and have examined the mouths of them for traces of moisture.  Mr. Farmiloe, a victim of destiny, could do nothing so reasonable.  Heedless of the fact that his shop remained unguarded, he seized his hat and rushed after the errand-boy.  If he could only have a sniff at the mixture it would either confirm his fear or set his mind at rest.  He tore along the road—­and was too late.  The boy met him, having just completed his errand.