Some of the members were one evening seated together in their clubhouse in the Adelphi. 
Those present were: Henry Melville, a barrister not overburdened with briefs, who was discussing a problem with Ernest Russell, a bearded man of middle age, who held some easy post in Somerset House, and was a Senior Wrangler and one of the most subtle thinkers of the club; 
Fred Wilson, a journalist of very buoyant spirits, who had more real capacity than one would at first suspect; 
John Macdonald, a Scotsman, whose record was that he had never solved a puzzle himself since the club was formed, though frequently he had put others on the track of a deep solution; 
Tim Churton, a bank clerk, full of cranky, unorthodox ideas as to perpetual motion; also Harold Tomkins, a prosperous accountant, remarkably familiar with the elegant branch of mathematics—the theory of numbers.

Suddenly Herbert Baynes entered the room, and everybody saw at once from his face that he had something interesting to communicate. Baynes was a man of private means, with no occupation.

"Here's a quaint little poser for you all," said Baynes. "I have received it to-day from Dovey."
Dovey was proprietor of one of the many private detective agencies that found it to their advantage to keep in touch with the club.

"Is it another of those easy cryptograms?" asked Wilson. 
"If so, I would suggest sending it upstairs to the billiard-marker."

"Don't be sarcastic, Wilson," said Melville. 
"Remember, we are indebted to Dovey for the great Railway Signal Problem that gave us all a week's amusement in the solving.

"If you fellows want to hear," resumed Baynes, "just try to keep quiet while I relate the amusing affair to you. 
You all know of the jealous little Yankee who married Lord Marksford two years ago? 
Lady Marksford and her husband have been in Paris for two or three months. 
Well, the poor creature soon got under the influence of the green-eyed monster, and formed the opinion that Lord Marksford was flirting with other ladies of his acquaintance.

"Now, she has actually put one of Dovey's spies on to that excellent husband of hers; and the myrmidon has been shadowing him about for a fortnight with a pocket camera. 
A few days ago he came to Lady Marksford in great glee. 
He had snapshotted his lordship while actually walking in the public streets with a lady who was not his wife."

"'What is the use of this at all?' asked the jealous woman.

"'Well, it is evidence, your ladyship, that your husband was walking with the lady. 
I know where she is staying, and in a few days shall have found out all about her.'

"'But, you stupid man,' cried her ladyship, in tones of great contempt, 'how can any one swear that this is his lordship, when the greater part of him, including his head and shoulders, is hidden from sight? 
And—and'—she scrutinized the photo carefully—'why, I guess it is impossible from this photograph to say whether the gentleman is walking with the lady or going in the opposite direction!'

"Thereupon she dismissed the detective in high dudgeon. 
Dovey has himself just returned from Paris, and got this account of the incident from her ladyship. 
He wants to justify his man, if possible, by showing that the photo does disclose which way the man is going. 
Here it is. See what you fellows can make of it."

Our illustration is a faithful drawing made from the original photograph. 
It will be seen that a slight but sudden summer shower is the real cause of the difficulty.

All agreed that Lady Marksford was right—that it is impossible to determine whether the man is walking with the lady or not.

"Her ladyship is wrong," said Baynes, after everybody had made a close scrutiny.
"I find there is important evidence in the picture. Look at it carefully."

"Of course," said Melville, "we can tell nothing from the frock-coat. It may be the front or the tails. Blessed if I can say! 
Then he has his overcoat over his arm, but which way his arm goes it is impossible to see."

"How about the bend of the legs?" asked Churton.

"Bend! why, there isn't any bend," put in Wilson, as he glanced over the other's shoulder. 
"From the picture you might suspect that his lordship has no knees. 
The fellow took his snapshot just when the legs happened to be perfectly straight."

"I'm thinking that perhaps——" began Macdonald, adjusting his eye-glasses.

"Don't think, Mac," advised Wilson. 
"It might hurt you. 
Besides, it is no use you thinking that if the dog would kindly pass on things would be easy. He won't."

"The man's general pose seems to me to imply movement to the left," Tomkins thought.

"On the contrary," Melville declared, "it appears to me clearly to suggest movement to the right."

"Now, look here, you men," said Russell, whose opinions always carried respect in the club.
"It strikes me that what we have to do is to consider the attitude of the lady rather than that of the man. 
Does her attention seem to be directed to somebody by her side?"

Everybody agreed that it was impossible to say.

"I've got it!" shouted Wilson. "Extraordinary that none of you have seen it. It is as clear as possible. 
It all came to me in a flash!"

"Well, what is it?" asked Baynes.

"Why, it is perfectly obvious. 
You see which way the dog is going—to the left. 
Very well. 
Now, Baynes, to whom does the dog belong?"

"To the detective!"

The laughter against Wilson that followed this announcement was simply boisterous, and so prolonged that Russell, who had at the time possession of the photo, seized the opportunity for making a most minute examination of it. 
In a few moments he held up his hands to invoke silence.

"Baynes is right," he said. 
"There is important evidence there which settles the matter with certainty. 
Assuming that the gentleman is really Lord Marksford—and the figure, so far as it is visible, is his I have no hesitation myself in saying that"

"Stop!" all the members shouted at once.

"Don't break the rules of the club, Russell, though Wilson did," said Melville. 
"Recollect that 'no member shall openly disclose his solution to a puzzle unless all present consent.'"

"You need not have been alarmed," explained Russell.
"I was simply going to say that I have no hesitation in declaring that Lord Marksford is walking in one particular direction. 
In which direction I will tell you when you have all 'given it up.'"

See answer