on the corner opposite dr. stuart's establishment stood a house which was "to be let or sold." from the estate-agent whose name appeared upon the notice-board i obtained the keys—and had a duplicate made of that which opened the front door. it was a simple matter, and the locksmith returned both keys to me within an hour. i informed the agent that the house would not suit me.

nevertheless, having bolted the door, in order that prospective purchasers might not surprise me, i "camped out" in an upper room all day, watching from behind the screen of trees all who came to the house of dr. stuart. dusk found me still at my post, armed with a pair of good binoculars. every patient who presented himself i scrutinized carefully, and finding as the darkness grew that it became increasingly difficult to discern the features of visitors, i descended to the front garden and resumed my watch from the lower branches of a tree which stood some twenty feet from the roadway.

at selected intervals i crept from my post and surveyed the lane upon which the window of the consulting-room opened and also the path leading to the tradesmen's entrance, from which one might look across the lawn and in at the open study windows. it was during one of these tours of inspection and whilst i was actually peering through a gap in the hedge, that i heard the telephone bell. dr. stuart was in the study and i heard him speaking.

i gathered that his services were required immediately at some institution in the neighbourhood. i saw him take his hat, stick and bag from the sofa and go out of the room. then i returned to the front garden of my vacant house.

no one appeared for some time. a policeman walked slowly up the road, and flashed his lantern in at the gate of the house i had commandeered. his footsteps died away. then, faintly, i heard the hum of a powerful motor. i held my breath. the approaching car turned into the road at a point above me to the right, came nearer … and stopped before dr. stuart's door.

i focussed my binoculars upon the chauffeur.

it was the brown-skinned man! nom d'un nom! a woman was descending form the car. she was enveloped in furs and i could not see her face. she walked up the steps to the door and was admitted.

the chauffeur backed the car into the lane beside the house.

my heart beating rapidly with excitement, i crept out by the further gate of the drive, crossed the road at a point fifty yards above the house and walking very quietly came back to the tradesmen's entrance. into its enveloping darkness i glided and on until i could peep across the lawn.

the elegant visitor, as i hoped, had been shown, not into the ordinary waiting-room but into the doctor's study. she was seated with her back to the window, talking to a grey-haired old lady—probably the doctor's housekeeper. impatiently i waited for this old lady to depart, and the moment that she did so, the visitor stood up, turned and … it was zara el-khala!

it was only with difficulty that i restrained the cry of triumph which arose to my lips. on the instant that the study door closed, zara el-khala began to try a number of keys which she took from her handbag upon the various drawers of the bureau!

"so!" i said—"they are uncertain of the drawer!"

suddenly she desisted, looking nervously at the open windows; then, crossing the room, she drew the curtains. i crept out into the road again and by the same roundabout route came back to the empty house. feeling my way in the darkness of the shrubbery, i found the motor bicycle which i had hidden there and i wheeled it down to the further gate of the drive and waited.

i could see the doctor's door, and i saw him returning along the road. as he appeared, from somewhere—-i could not determine from where—came a strange and uncanny wailing sound, a sound that chilled me like an evil omen.

even as it died away, and before dr. stuart had reached his door i knew what it portended—that horrible wail. some one hidden i knew not where, had warned zara el-khala that the doctor returned! but stay! perhaps that some one was the dark-skinned chauffeur!

how i congratulated myself upon the precautions which i had taken to escape observation. evidently the watcher had placed himself somewhere where he could command a view of the front door and the road.

five minutes later the girl came out, the old housekeeper accompanying her to the door, the car emerged from the lane, zara el-khala entered it and was driven away. i could see no one seated beside the chauffeur. i started my "indian" and leapt in pursuit.

as i had anticipated, the route was eastward, and i found myself traversing familiar ground. from the south-west to the east of london whirled the big car of mystery—and i was ever close behind it. sometimes, in the crowded streets, i lost sight of my quarry for a time, but always i caught up again, and at last i found myself whirling along commercial road and not fifty yards behind the car.

just by the canal bridge a drunken sailor lurched out in front of my wheel, and only by twisting perilously right into a turning called, i believe, salmon lane, did i avoid running him down.

sacre nom! how i cursed him! the lane was too narrow for me to turn and i was compelled to dismount and to wheel my "indian" back to the highroad. the yellow car had vanished, of course, but i took it for granted that it had followed the main road. at a dangerous speed, pursued by execrations from the sailor and all his friends, i set off east once more turning to the right down west india dock road.

arriving at the dock, and seeing nothing ahead of me but desolation and ships' masts, i knew that that inebriated pig had spoiled everything! i could have sat down upon the dirty pavement and wept, so mortified was i! for if zara el-khala had secured the envelope i had missed my only chance.

however, pardieu! i have said that despair is not permitted by the bureau. i rode home to my hotel, deep in reflection. whether the girl had the envelope or not, at least she had escaped detection by the doctor; therefore if she had failed she would try again. i could sleep in peace until the morrow.

of the following day, which i spent as i had spent the preceding one, i have nothing to record. at about the same time in the evening the yellow car again rolled into view, and on this occasion i devoted all my attention to the dark-skinned chauffeur, upon whom i directed my glasses.

as the girl alighted and spoke to him for a moment, he raised the goggles which habitually he wore and i saw his face. a theory which i had formed on the previous night proved correct. the chauffeur was the hindu, chunda lal! as zara el-khala walked up the steps he backed the car into the narrow lane and i watched him constantly. yet, watch as closely as i might, i could not see where he concealed himself in order to command a view of the road.

on this occasion, as i know, dr. stuart was at home. nevertheless, the girl stayed for close upon half an hour, and i began to wonder if some new move had been planned. suddenly the door opened and she came out.

i crept through the bushes to my bicycle and wheeled it on to the drive. i saw the car start; but madame fortune being in playful mood, my own engine refused to start at all, and when ten minutes later i at last aroused a spark of life in the torpid machine i knew that pursuit would be futile.

since this record is intended for the guidance of those who take up the quest of "the scorpion" either in co-operation with myself or, in the event of my failure, alone, it would be profitless for me to record my disasters. very well, i had one success. one night i pursued the yellow car from dr. stuart's house to the end of limehouse causeway without once losing sight of it.

a string of lorries form the docks, drawn by a traction engine, checked me at the corner for a time, although the yellow car passed. but i raced furiously on and by great good luck overtook it near the dock station. from thence onward pursuing a strangely tortuous route, i kept it in sight to canning town, when it turned into a public garage. i followed—to purchase petrol.

chunda lal was talking to the man in charge; he had not yet left his seat. but the car was empty!

at first i was stupid with astonishment. par la barbe du prophete! i was astounded. then i saw that i had really made a great discovery. the street into which i had injudiciously followed "le balafre" lay between limehouse causeway and ropemaker street, and it was at no great distance from this point that i had lost sight of the yellow car. in that street, which according to my friend the policeman was "nearly all chinese," zara el-khala had descended; in that street was "the scorpion's" lair!