“Quite neat, in its little conventional way,” he said.  “It’s on the regular English pattern.  Our acrostics are a trifle smarter, but all run into one form.  The great acrostic writer isn’t born.  If acrostics were as big a thing as chess, then we should have masters who would produce masterpieces.”

“But this one—­d’you see it?”

“Milk for babes, Mark.”

Mr. Ganns turned to his notebook, wrote swiftly into it, tore out the page, and handed the solution to his companion.

Brendon read: 

G      O      D
Omega  Alph   A
D      O      G

“If you know Knut Hamsun’s stories, then you guess it instantly.  If not, you might possibly be bothered,” he said, while Brendon stared.

“There are two ways with acrostics,” continued Peter, full of animation, “the first is to make lights so difficult that they turn your hair grey till you’ve got them, the second—­just traps—­perhaps three perfectly sound answers to the same light, but the second just a shade sounder than the first, and the third a shade sounder than either of the others.”

“Who makes acrostics like that?”

“Nobody.  Life’s too short; but if I devoted a year to a perfect acrostic, you bet your life it would take my fellow creatures a year to guess it.  The same with cryptography, which we’ve both run up against, no doubt, in course of business.  Cyphers are mostly crude; but I’ve often thought what a right down beauty it might be possible to make, given a little pains.  The detective story writers make very good ones sometimes; but then the smart man, who wipes everybody’s eyes, always gets ’em—­by pulling down just the right book from the villain’s library.  My cryptograph won’t depend on books.”

Peter chattered on; then he suddenly stopped and turned to his notes again.

He looked up presently.

“The hard thing before us is this,” he said, “to get into touch with Robert Redmayne, or his ghost.  There are two sorts of ghost, Mark; the real thing—­in which you don’t believe and concerning which I hold a watching brief; and the manufactured article.  Now the manufactured article can be quite as useful to the bulls as the crooks.”

“You believe in ghosts!”

“I didn’t say so.  But I keep an open mind.  I’ve heard some funny things from men whose word could be relied upon.”

“If this is a ghost, that’s a way out, of course; but in that case why are you frightened for Albert Redmayne’s life?”

“I don’t say he’s a ghost and of course I don’t think he’s a ghost; but—­”

He broke off and changed the subject.