s
inconspicuously employed all the time. But occasionally a more exacting
demand will be made on it. It may be in a homicide case in which a wife
has poisoned her husband.

Of course, in a case of this sort, "stool pigeon" men are useless, for
no professional crooks are involved. So Manning assigns six or seven of
his best men to the case. They do not roam about promiscuously, treading
on one another's toes. To each is given a phase of the case to develop
and he reports as frequently as possible to the chief. At the end of
four weeks Manning, surveying the reports of his men, finds himself in
possession of the following:

The chemical analysis of the vital organs shows that the victim died of
arsenic poisoning. Detectives have discovered the druggist who sold the
poison to the wife. Other detectives have turned in competent evidence
tending to establish the woman's dislike of her husband. Moreover, she
was in love with another man in whose company she was frequently seen.
Then it is found that the husband's life was insured and his death not
only released her from matrimonial ties which had become irksome, but
also netted her a considerable sum in cash.

Sufficient motive for the crime has now been established. The poison of
which the husband died has been traced directly to the wife. But a vital
element of the case is still missing. It is necessary to prove that the
wife had exclusive opportunity to administer the drug.

Manning now concentrates all his energies toward this end. Obviously,
all the deductions of Messrs. Lecocq and Sherlock Holmes would be
futile. But through shrewd questioning of the servants in the house he
ascertains that the husband was taken violently ill after supper and
that no guests were present at the meal.

An analysis of the sediment in the husband's coffee cup establishes the
presence of arsenic. It must be inferred that the wife's cup contained
none of the poison, for she developed no symptoms of poisoning after the
meal.

The servants declare that the wife invariably made the after-dinner
coffee in a percolator that stood on the sideboard. On the night in
question, she had boiled the coffee, but none of the servants had seen
her draw it from the percolator or serve it in the cups. But all of them
assert that for a year or more it had been the wife's custom to do the
serving, so it is a fair inference that the husband did not leave his
seat at the table to help himself to coffee, on