It was underground.  
In that dank cavern down below Belgrave Square the walls were dripping. But what was that to the magician? It was secrecy that he needed, not dryness. There he pondered upon the trend of events, shaped destinies and concocted magical brews.
 
For the last few years the serenity of his ponderings had been disturbed by the noise of the motor-bus; while to his keen ears there came the earthquake-rumble, far off, of the train in the tube, going down Sloane Street; and when he heard of the world above his head was not to its credit.
 
He decided one evening over his evil pipe, down there in his dank chamber, that London had lived long enough, had abused its opportunities, had gone too far, in fine, with its civilisation. And so he decided to wreck it.
 
Therefore he beckoned up his acolyte from the weedy end of the cavern, and, "Bring me," he said, "the heart of the toad that dwelleth in Arabia and by the mountains of Bethany." The acolyte slipped away by the hidden door, leaving that grim old man with his frightful pipe, and whither he went who knows but the gipsy people, or by what path he returned; but within a year he stood in the cavern again, slipping secretly in by the trap while the old man smoked, and he brought with him a little fleshy thing that rotted in a casket of pure gold.
 
"What is it?" the old man croaked.
 
"It is," said the acolyte, "the heart of the toad that dwelt once in Arabia and by the mountains of Bethany."
 
The old man's crooked fingers closed on it, and he blessed the acolyte with his rasping voice and claw-like hand uplifted; the motor-bus rumbled above on its endless journey; far off the train shook Sloane Street.
 
"Come," said the old magician, "it is time." And there and then they left the weedy cavern, the acolyte carrying cauldron, gold poker and all things needful, and went abroad in the light. And very wonderful the old man looked in his silks.
 
Their goal was the outskirts of London; the old man strode in front and the acolyte ran behind him, and there was something magical in the old man's stride alone, without his wonderful dress, the cauldron and............