I suppose it was, perhaps, a quarter of an hour later when we turned into the thoroughfare down the centre of which runs the railway in a deep cutting. The houses were large ones, let out in fine flats, the residences mostly of the professional and wealthier tradesman classes.
We went along, until presently I caught sight of another taxi standing at the kerb. Therefore I dismissed mine, and, keeping well in the shadow, sauntered along the boulevard, now quiet and deserted.
With great precaution I approached the standing taxi on the opposite side of the way. There was nobody within. It was evidently awaiting some one, and as it was the only one in sight I concluded that it must be the same which Sylvia had taken from the hotel.
Some distance further on I walked, when, before me, I recognized her neat figure, and almost a moment afterwards saw her disappear into a large doorway which was in complete darkness—the doorway of what seemed to be an untenanted house.
I halted quickly and waited—yet almost ashamed of myself for spying thus.
A moment later I saw that, having believed herself unobserved, she struck a match, but for what reason did not seem apparent. She appeared to be examining the wall. She certainly was not endeavouring to open the door. From the distance, however, I was unable to distinguish very plainly.
The vesta burned out, and she threw it upon the ground. Then she hurriedly retraced her steps to where she had left her cab, and I was compelled to bolt into a doorway in order to evade her.
She passed quite close to me, and when she had driven away I emerged, and, walking to the doorway, also struck a light and examined the same stone wall. At first I could discover nothing, but after considerable searching my eyes at last detected a dark smudge, as though something had been obliterated.
It was a cryptic sign in lead pencil, and apparently she had drawn her hand over it to remove it, but had not been altogether successful. Examining it closely, I saw that the sign, as originally scrawled upon the smooth stone, was like two crescents placed back to back, while both above and below rough circles had been drawn.