"Good!" he said quietly. "Good! And now, then--the critical question! For whom?"
"For a Dr. Charles Ambrose, from a prescription of his own," replied Macpherson. "It's a sort of pick-me-up tonic. I first made it up for him two years ago; I've made it up for him several times since. The last occasion was about six weeks ago. I have all the dates, though, in my books; I can show you them."
"Wait a bit," said Matherfield. "That's of no great importance--yet. Dr. Charles Ambrose, eh? Have you his address?"
"Aye, to be sure!" answered the chemist. "His address is 38, Number 59, John Street."
"Adelphi, precisely--38, Number 59, John Street, Adelphi," repeated Macpherson. "That's in the books, too."
Matherfield suddenly became silent, staring at the floor. When he looked up again it was at Hetherwick.
"Didn't Granett exclaim that he knew of a doctor, close by, when he rushed out of that train at Charing Cross Underground?" he asked. "Gave the impression that he knew of one close by, anyway?"
"He said distinctly close by," answered Hetherwick. "Why, are you thinking----"
Matherfield interrupted him with a wave of the hand, and turned again to the chemist. "You've seen this Dr. Charles Ambrose?" he asked abruptly.
"Oh, I have, Mr. Matherfield, many a time and often," replied Macpherson. "But now I come to think of it, not lately."
"I should think last when he called in and told me to make him another bottle of his tonic," answered Macpherson, after some thought. "As I said just now, perhaps about six weeks ago. But the books----"
"Never mind the books yet. What's this Dr. Charles Ambrose like?"
"A tall, handsome man, distinguished-looking--I should say about forty years of age. A dark man--hair, eyes, beard. He wears his moustache and beard in--well, a sort of foreign fashion; in fact, he's more like a Spaniard than an Englishman."
"He was always taken by me for an Englishman; he speaks like one--that is, like an Englishman of the upper classes. He once told me he was an Oxford man--we'd been talking about universities."
"Did you ever see him in a big, dark overcoat, with a large white silk muffler about his neck and the lower part of his face?"
"Aye, I've seen him like that! On chilly evenings. Indeed, that's another thing he told me--he was subject to bronchial attacks."