The watery eyes of the cabman protruded painfully; he respired like a horse.

“Me, guv’nor!” he exclaimed.  “Gor’blime!  I ain’t the bloke!  I was drivin’ back from takin’ the Honorable ’Erbert ’Arding ’ome—­same as I does almost every night, when the ’ouse is a-sittin’—­when I see old Tom Brian drawin’ away from the door o’ Palace Man—­”

Again Dunbar held up his hand.

“No doubt you mean well,” he said; “but damme! begin at the beginning!  Who are you, and what have you come to tell us?”

“’Oo are I?—­’Ere’s ’oo I ham!” wheezed the cabman, proffering a greasy license.  “Richard ’Amper, number 3 Breams Mews, Dulwich Village"...

“That’s all right,” said Dunbar, thrusting back the proffered document; “and last night you had taken Mr. Harding the member of Parliament, to his residence in?”—­

“In Peers’ Chambers, Westminister—­that’s it, guv’nor!  Comin’ back, I ‘ave to pass along the north side o’ the Square, an’ just a’ead o’ me, I see old Tom Brian a-pullin’ round the Johnny ‘Orner,—­’im comin’ from Palace Mansions.”

“Mr. Exel only mentioned seeing one cab,” muttered Dunbar, glancing keenly aside at Sowerby.

“Wotcher say, guv’nor?” asked the cabman.

“I say—­did you see a gentleman approaching from the corner?” asked Dunbar.

“Yus,” declared the man; “I see ’im, but ’e ’adn’t got as far as the Johnny ‘Orner.  As I passed outside old Tom Brian, wot’s changin’ ’is gear, I see a bloke blowin’ along on the pavement—­a bloke in a high ‘at, an’ wearin’ a heye-glass.”

“At this time, then,” pursued Dunbar, “you had actually passed the other cab, and the gentleman on the pavement had not come up with it?”

“‘E couldn’t see it, guv’nor!  I’m tellin’ you ’e ’adn’t got to the Johnny ’Orner!”

“I see,” muttered Sowerby.  “It’s possible that Mr. Exel took no notice of the first cab—­especially as it did not come out of the Square.”

“Wotcher say, guv’nor?” queried the cabman again, turning his bleared eyes upon Sergeant Sowerby.

“He said,” interrupted Dunbar, “was Brian’s cab empty?”

“’Course it was,” rapped Mr. Hamper, “’e ’d just dropped ’is fare at Palace Mansions."...

“How do you know?” snapped Dunbar, suddenly, fixing his fierce eyes upon the face of the speaker.

The cabman glared in beery truculence.

“I got me blarsted senses, ain’t I?” he inquired.  “There’s only two lots o’ flats on that side o’ the Square—­Palace Mansions, an’ St. Andrew’s Mansions.”

“Well?”

“St. Andrew’s Mansions,” continued Hamper, “is all away!”

“All away?”

“All away!  I know, ’cause I used to have a reg’lar fare there.  ’E’s in Egyp’; flat shut up.  Top floor’s to let.  Bottom floor’s two old unmarried maiden ladies what always travels by ’bus.  So does all their blarsted friends an’ relations.  Where can old Tom Brian ‘ave been comin’ from, if it wasn’t Palace Mansions?”