a safe and
leave it open!" he had said to himself. This little key, with its brass
head and complicated wards, had strongly attracted him,--its presence
had suggested robbery.

Monsieur de Marquet appeared to be greatly perplexed, as if he did
not know whether he ought to be glad of the new direction given to the
inquiry by the young reporter, or sorry that it had not been done by
himself. In our profession and for the general welfare, we have to put
up with such mortifications and bury selfish feelings. That was why
Monsieur de Marquet controlled himself and joined his compliments with
those of Monsieur Dax. As for Monsieur Rouletabille, he simply shrugged
his shoulders and said: "There's nothing at all in that!" I should have
liked to box his ears, especially when he added: "You will do well,
Monsieur, to ask Monsieur Stangerson who usually kept that key?"

"My daughter," replied Monsieur Stangerson, "she was never without it.

"Ah! then that changes the aspect of things which no longer corresponds
with Monsieur Rouletabille's ideas!" cried Monsieur de Marquet. "If that
key never left Mademoiselle Stangerson, the murderer must have waited
for her in her room for the purpose of stealing it; and the robbery
could not have been committed until after the attack had been made on
her. But after the attack four persons were in the laboratory! I can't
make it out!"

"The robbery," said the reporter, "could only have been committed before
the attack upon Mademoiselle Stangerson in her room. When the murderer
entered the pavilion he already possessed the brass-headed key."

"That is impossible," said Monsieur Stangerson in a low voice.

"It is quite possible, Monsieur, as this proves."

And the young rascal drew a copy of the "Epoque" from his pocket, dated
the 21st of October (I recall the fact that the crime was committed on
the night between the 24th and 25th), and showing us an advertisement,
he read:

"'Yesterday a black satin reticule was lost in the Grands Magasins de
la Louvre. It contained, amongst other things, a small key with a brass
head. A handsome reward will be given to the person who has found it.
This person must write, poste restante, bureau 40, to this address: M.
A. T. H. S. N.' Do not these letters suggest Mademoiselle Stangerson?"
continued the reporter. "The 'key with a brass head'--is not this
the key? I always read advertisements. In my business, as in yours,
Monsieur, one should always read