Chapter 1

Professor William James Maynard was in a singularly happy and contented
mood as he strolled down the High Street after a long and satisfactory
interview with the solicitor to his late cousin, whose sole heir he was.

It was exactly a month by the calendar since he had murdered this
cousin, and everything had gone most satisfactorily since. The fortune
was proving quite as large as he had expected, and not even an inquest
had been held upon the dead man. The coroner had decided that it was not
necessary, and the Professor had agreed with him.

At the funeral the Professor had been the principal mourner, and the
local paper had commented sympathetically on his evident emotion. This
had been quite genuine, for the Professor had been fond of his relative,
who had always been very good to him. But still, when an old man remains
obstinately healthy, when his doctor can say with confidence that he is
good for another twenty years at least, and when he stands between you
and a large fortune which you need, and of which you can make much
better use in the cause of science and the pursuit of knowledge, what
alternative is there? It becomes necessary to take steps. Therefore, the
Professor had taken steps.

Looking back to-day on that day a month ago, and the critical preceding
week, the Professor felt that the steps he had taken had been as
judicious as successful. He had set himself to solve a problem in higher
mathematics. He had found it easier to solve than many he was obliged to
grapple with in the course of his studies.

A policeman saluted as the Professor passed, and he acknowledged it with
the charming old world courtesy that made him so popular a figure in the
town. Across the way was the doctor who had certified the cause of
death. The Professor, passing benevolently on, was glad he had now
enough money to carry out his projects. He would be able to publish at
once his great work on "The Secondary Variation of the Differential
Calculus," that hitherto had languished in manuscript. It would make a
sensation, he thought; there was more than one generally accepted theory
he had challenged or contradicted in it. And he would put in hand at
once his great, his long projected work, "A History of the Higher
Mathematics." It would take twenty years to complete, it would cost
twenty thousand pounds or more, and it would breathe into mathematics
the new, vivid life that Bergson's works have breathed into
metaphysics.

The Professor thought very kindly of the dead cousin, whose money would
provide for this great work. He wished greatly the dead man could know
to what high use his fortune was designed.

Coming towards him he saw the wife of the vicar of his parish. The
Professor was a regular church-goer. The vicar's wife saw him, too, and
beamed. She and her husband were more than a little proud of having so
well known a man in their congregation. She held out her hand and the
Professor was about to take it when she drew it back with a startled
movement.

"Oh, I beg your pardon!" she exclaimed, distressed, as she saw him raise
his eyebrows. "There is blood on it."

Her eyes were fixed on his right hand, which he was still holding out.
In fact, on the palm a small drop of blood showed distinctly against the
firm, pink flesh. Surprised, the Professor took out his handkerchief and
wiped it away. He noticed that the vicar's wife was wearing white kid
gloves.

"Oh, I beg your pardon!" she said again. "It--it startled me somehow. I
thought you must have cut yourself. I hope it's not much?"

"Some scratch, I suppose," he said. "It's nothing."

The vicar's wife, still slightly discomposed, launched out into some
parochial matter she had wished to mention to him. They chatted a few
moments and then parted. The Professor took an opportunity to look at
his hand. He could detect no sign of any cut or abrasion, the skin
seemed whole everywhere. He looked at his handkerchief. There was still
visible on it the stain where he had wiped his hand, and this stain
seemed certainly blood.

"Odd!" he muttered as he put the handkerchief back in his pocket. "Very
odd!"

His thoughts turned again to his projected "A History of the Higher
Mathematics," and he forgot all about the incident till, as it happened
that day month, the first of the month by the calendar, when he was
sitting in his study with an eminent colleague to whom he was explaining
his great scheme.

"If you are able to carry it out," the colleague said slowly, "your book
will mark an epoch in human thought. But the cost will be tremendous."

"I estimate it at twenty thousand pounds," answered the Professor
calmly. "I am fully prepared to spend twice as much. You know I have
recently inherited forty thousand pounds from a relative?"

The eminent colleague nodded and looked very impressed.

"It is magnificent," he said warmly, "magnificent." He added: "You've
cut yourself, do you know?"

"Cut myself?" the Professor echoed, surprised.

"Yes," answered the eminent colleague, "there is blood upon your
hand--your right hand."

In fact a spot of blood, slightly larger than that which had appeared
before, showed plainly upon the Professor's right hand. He wiped it away
with his handkerchief, and went on talking eagerly, for he was deeply
interested. He did not think of the matter again till just as he was
getting into bed, when he noticed a red stain upon his handkerchief. He
frowned and examined his hand carefully. There was no sign of any wound
or cut from which the blood could have come, and he frowned again.

"Very odd!" he muttered.

A calendar hanging on the wall reminded him that it was the first of the
month.

The days passed, the incident faded from his memory, and four weeks
later he came down one morning to breakfast in an unusually good temper.
There was a certain theory he had worked on the night before he meant to
write to a friend about. It seemed to him his demonstration had been
really brilliant, and then, also, he was already planning out with great
success the details of the scheme for his great work.

He was making an excellent breakfast, for his appetite was always good,
and, needing some more cream, he rang the bell. The maid appeared, he
showed her the empty jug, and as she took it she dropped it with a
sudden cry, smashing it to pieces on the floor. Very pale, she stammered
out:

"Beg pardon, sir, your hand--there is blood upon your hand."

In fact, on the Professor's right hand there showed a drop of blood,
perceptibly larger this time than before. The Professor stared at it
stupidly. He was sure it had not been there a moment before, and he
noticed by the heading of the newspaper at the side of his plate that
this was the first of the month.

With a hasty movement of his napkin he wiped the drop of blood away. The
maid, still apologising, began to pick up the pieces of the jug she had
broken; but the Professor had no further appetite for his breakfast. He
silenced her with a gesture, and, leaving a piece of toast half-eaten on
his plate, he got up and went into his study.

All this was trivial, absurd even. Yet somehow it disturbed him. He got
out a magnifying glass and examined his hand under it. There was nothing
to account for the presence of the drop of blood he and the maid had
seen. It occurred to him that he might have cut himself in shaving; but
when he looked in the mirror he could find no trace of even the
slightest wound.

He decided that, though he had not been aware of it, his nerves must be
a little out of order. That was disconcerting. He had not taken his
nerves into consideration for the simple reason that he had never known
that he possessed any. He made up his mind to treat himself to a holiday
in Switzerland. One or two difficult ascents might brace him up a bit.

Three days later he was in Switzerland, and a few days later again he
was on the summit of a minor but still difficult peak. It had been an
exhilarating climb, and he had enjoyed it. He said something laughingly
to the head guide to the effect that climbing was good sport and a fine
test for the nerves. The head guide agreed, and added politely that if
the nerves of monsieur the Professor had shown signs of failing on the
lower glacier, for example, they might all have been in difficulties.
The Professor thrilled with pleasure at the head guide's implied praise.
He was glad to know on such good authority that his nerves were all
right, and the incidents that had driven him there began to fade in his
memory.

Nevertheless, he found himself watching the calendar with a certain
interest, and when he woke on the morning of the first day of the next
month he glanced quickly at his right hand. There was nothing there.

He dressed and spent, as he had planned, a quiet day, busy with his
correspondence. His spirits rose as the day passed. He was still
watchful, but more confident; and, after dinner, though he had meant to
go straight to his room, he agreed to join in a suggested game of
bridge. They were cutting for partners when one of the ladies who was to
take part in the game dropped with a little cry the card she had just
lifted.

"Oh, there is blood upon your hand," she cried, "on your right hand,
Professor!"

Upon the Professor's right hand there showed now a drop of blood, larger
still then those other three had been. Yet the very moment before it had
not been there. The Professor put down his cards without a word, and
left the room, going straight upstairs.

The drop of blood was still standing on his hand. He soaked it up
carefully with some cotton-wool he had, and was not surprised to find
beneath no sign or trace of any cut or wound. The cotton-wool he made up
carefully into a parcel and addressed it to an analytical chemist he
knew, inclosing with it a short note.

He rang the bell, sent the parcel to the post, and then he got out pen
and paper and set himself to solve this problem, as in his life he had
solved so many others.

Only this time it seemed somehow as though the data were insufficient.

Idly his pen traced upon the paper in front of him a large _X_, the sign
of the unknown quantity.

But how, in this case, to find out what was the unknown quantity? His
hand, his firm and steady hand, shook so that he could no longer hold
his pen. He rang the bell again and ordered a stiff whisky-and-soda. He
was a man of almost ascetic habits, but to-night he felt that he needed
some stimulant.

Neither did he sleep very well.

The next day he returned to England. Almost at once he went to see his
friend, the analytical chemist, to whom he had sent the parcel from
Switzerland.

"Mammalian blood," pronounced the chemist, "probably human--rather a
curious thing about it, too."

"What's that?" asked the Professor.

"Why," his friend answered, "I was able to identify the distinctive
bacillus----" He named the rare bacillus of an unusual and obscure
disease. And this disease was that from which the Professor's cousin had
died.

The professor was a man interested in all phenomena. In other
circumstances he would have observed keenly that which now occurred,
when the hair of his head underwent a curious involuntary stiffening and
bristling process that in popular but sufficiently accurate terms, might
be described as "standing on end." But at the moment he was in no state
for scientific observations.

He got out of the house somehow. He said he did not feel well, and his
friend, the chemist, agreed that his holiday in Switzerland did not seem
to have done him much good.

The Professor went straight home and shut himself up in his study. It
was a fine room, ranged all round with books. On the shelves nearest to
his hand stood volumes on mathematics, the theory of mathematics, the
study of mathematics, pure mathematics, applied mathematics. But there
was not any one of these books that told him anything about such a thing
as this. Though, it is true, there were many references in them, here
and there, to _X_, the unknown quantity.

The Professor took his pen and wrote a large _X_ upon the sheet of paper
in front of him.

"An unknown quantity!" he muttered. "An unknown--quantity!"

The days passed peacefully. Nothing was out of the ordinary except that
the Professor developed an odd trick of continually glancing at his
right hand. He washed it a good deal, too. But the first of the month
was not yet.

On the last day of the month he told his housekeeper that he was feeling
a little unwell. She was not surprised, for she had thought him looking
ill for some time past. He told her he would probably spend the next day
in bed for a thorough rest, and she agreed that that would be a very
good idea. When he was in his own room and had undressed, he bandaged
his right hand with care, tying it up carefully and thoroughly with
three or four of his large linen handkerchiefs.

"Whatever comes, shall now show," he said to himself.

He stayed in bed accordingly the next day. His housekeeper was a little
uneasy about him. He ate nothing and his eyes were strangely bright and
feverish. She overheard him once muttering something to himself about
"the unknown quantity," and that made her think that he had been working
too hard.

She decided he must see the doctor. The Professor refused peremptorily.
He declared he would be quite well again in the morning. The
housekeeper, an old servant, agreed, but sent for the doctor all the
same; and when he had come the Professor felt he could not refuse to see
him without appearing peculiar. And he did not wish to appear peculiar.
So he saw the doctor, but declared there was nothing much the matter, he
merely felt a little unwell and out of sorts and tired.

"You have hurt your hand?" the doctor asked, noticing how it was
bandaged.

"I cut it slightly--a trifle," the Professor answered.

"Yes," the doctor answered, "I see there is blood on it."

"What?" the Professor stammered.

"There is blood upon your hand," the doctor repeated.

The Professor looked. In fact, a deep, wide stain showed crimson upon
the bandages in which he had swathed his hand. Yet he knew that the
moment before the linen had been fair and white and clean.

"It is nothing," he said quickly, hiding his hand beneath the bed
clothes.

The doctor, a little puzzled, took his leave, but had not gone ten
yards when the housekeeper flew screaming after him. It seemed she had
heard a fall, and when she had gone into the Professor's bedroom she had
found him lying there dead upon the hearthrug. There was a razor in his
hand, and there was a ghastly gash across his throat.

The doctor went back at a run, but there was nothing he or any man could
do. One thing he noticed, with curiosity, was that the bandage had been
torn away from the dead man's hand and that oddly enough there seemed to
be on the hand no sign of any cut or wound. There was a large solitary
drop of blood on the palm, at the root of the thumb; but, of course,
that was no great wonder, for the wound the dead man had dealt himself
had bled freely.

Apparently death had not been quite instantaneous, for with a last
effort the Professor seemed to have traced an _X_ upon the floor in his
own blood with his forefinger. The doctor mentioned this at the
inquest--the coroner had decided at once that in this case an inquest
was certainly necessary--and he suggested that it showed the Professor
had worked too hard and was suffering from overwork which had disturbed
his mental balance.

The coroner took the same view, and in his short address to the jury
adduced the incident as proof of a passing mental disturbance.

"Very probably," said the coroner, "there was some problem that had
worried him, and that he was still endeavouring to work out. As you are
aware, gentlemen, the sign _X_ is used to symbolise the unknown
quantity."

An appropriate verdict was accordingly returned, and the Professor was
duly interred in the same family vault as that in which so short a time
previously his cousin had been laid to rest.