martin hackness dressed with less than his usual care that evening. he even forgot that miss cynthia grimfern had a strong prejudice in favour of black evening ties, and, usually, he paid a great deal of deference to her opinions. but he was thinking of other matters now.

there was no sign of anything abnormal as hackness drove along in the direction of clarence terrace. the night was more than typically yellow for the time of year, but there was no kind of trouble with the traffic though down the river the fairway lay under a dense bank of cloud.

hackness sniffed the air eagerly. he detected or thought he detected a certain acrid suggestion in the atmosphere. as the cab approached trafalgar square hackness could hear shouts and voices raised high in protestation. suddenly his cab seemed to be plunged into a wall of darkness.

it was so swift and unexpected that it came with the force of a blow. the horse appeared to have trotted into a bank of dense blackness. the wall had shut down so swiftly, blotting out a section of london, that hackness could only gaze at it with mouth wide open.

hackness hopped out of his cab hurriedly. so sheer and stark was the black wall that the horse was out of sight. mechanically the driver reined back. the horse came back to the cab with the dazzling swiftness of a conjuring trick. a thin stream of breeze wandered from the direction of whitehall. it was this air finding its way up the funnel formed by the sheet that cut off the fog to a razor edge.

"been teetotal for eighteen years," the cabman muttered, "so that's all right. and what do you please to make of it, sir?"

hackness muttered something incoherent. as he stood there, the black wall lifted like a stage curtain, and he found himself under the lee of an omnibus. in a dazed kind of way he patted the cabhorse on the flank. he looked at his hand. it was greasy and oily and grimy as if he had been in the engine-room of a big liner.

"get on as fast as you can," he cried. "it was fog, just a little present from the burning petroleum. anyway, it's gone now."

true, the black curtain had lifted, but the atmosphere reeked with the odour of burning oil. the lamps and shop windows were splashed and mottled with something that might have passed for black snow. traffic had been brought to a standstill for the moment, eager knots of pedestrians were discussing the situation with alarm and agitation, a man in evening dress was busily engaged in a vain attempt to remove sundry black patches from his shirt front.

sir edgar grimfern was glad to see his young friend. had grimfern been comparatively poor, and less addicted to big game shooting, he would doubtless have proved a great scientific light. anything with a dash of adventure fascinated him. he was enthusiastic on flying machines and aeroplanes generally. there were big work-shops at the back of 119, clarence terrace, where hackness put in a good deal of his spare time. those two were going to startle the world presently.

hackness shook hands thoughtfully with cynthia grimfern. there was a slight frown on her pretty intellectual face as she noted his tie.

"there's a large smut on it," she remarked, "and it serves you right."

hackness explained. he had a flattering audience. he told of the strange happening in trafalgar square and the majestic scene on the river. he gave a graphic account of the theory that he had built upon it. there was an animated discussion all through dinner.

"the moral of which is that we are going to be plunged into cimmerian darkness," cynthia said, "that is, if the fog comes down. if you think you are going to frighten me out of my evening's entertainment you are mistaken."

all the same it had grown much darker and thicker as the trio drove off in the direction of the lyceum theatre. there were patches of dark acrid fog here and there like ropes of smoke into which figures passed and disappeared only to come out on the other side choking and coughing. so local were these swathes of fog that in a wide thoroughfare it was possible to partially avoid them. festoons of vapour hung from one lamp-post to another, the air was filled with a fatty sickening odour.

"how nasty," cynthia exclaimed. "mr. hackness, please close that window. i am almost sorry that we started. what's that?"

there was a shuffling movement under the seat of the carriage, the quick bark of a dog; cynthia's little fox terrier had stolen into the brougham. it was a favourite trick of his, the girl explained.

"he'll go back again," she said. "kim knows that he has done wrong."

that kim was forgotten and discovered later on coiled up under the stall of his mistress was a mere detail. hackness was too preoccupied to feel any uneasiness. he was only conscious that the electric lights were growing dim and yellow, and that a brown haze was coming between the auditorium and the stage. when the curtain fell on the third act it was hardly possible to see across the theatre. two or three large heavy blots of some greasy matter fell on to the white shoulders of a lady in the stalls to be hastily wiped away by her companion. they left a long greasy smear behind.

"i can hardly breathe," cynthia gasped. "i wish i had stopped at home. surely those electric lights are going out."

but the lights were merely being wrapped in a filament that every moment grew more and more dense. as the curtain went up again there was just the suspicion of a draught from the back of the stage, and the whole of it was smothered in a small brown cloud that left absolutely nothing to the view. it was impossible now to make out a single word of the programme, even when it was held close to the eyes.

"hackness was right," grimfern growled. "we had far better have stayed at home."

hackness said nothing. he had no pride in the accuracy of his forecast. perhaps he was the only man in london who knew what the full force of this catastrophe meant. it grew so dark now that he could see no more than the mere faint suggestion of his fair companion, something was falling out of the gloom like black ragged snow. as the pall lifted just for an instant he could see the dainty dresses of the women absolutely smothered with the thick oily smuts. the reek of petroleum was stifling.

there was a frightened scream from behind, and a yell out of the ebony wall to the effect that somebody had fainted. someone was speaking from the stage with a view to stay what might prove to be a dangerous panic. another sombre wave filled the theatre and then it grew absolutely black, so black that a match held a foot or so from the nose could not be seen. one of the plagues of egypt with all its horrors had fallen upon london.

"let us try and make our way out," hackness suggested. "go quietly."

others seemed to be moved by the same idea. it was too black and dark for anything like a rush, so that a dangerous panic was out of the question. slowly but surely the fashionable audience reached the vestibule, the hall, and the steps.

nothing to be seen, no glimmer of anything, no sound of traffic. the destroying angel might have passed over london and blotted out all human life. the magnitude of the disaster had frightened london's millions as it fell.