“With a quick thrust—­she’s a big woman and a bold one—­she strikes.  Possibly Hotchkiss is right about the left-hand blow.  Harrington may have held her right hand, or perhaps she held the dirk in her left hand as she groped with her right.  Then, as the man falls back, and his grasp relaxes, she straightens and attempts to get away.  The swaying of the car throws her almost into your berth, and, trembling with terror, she crouches behind the curtains of lower ten until everything is still.  Then she goes noiselessly back to her berth.”

I nodded.

“It seems to fit partly, at least,” I said.  “In the morning when she found that the crime had been not only fruitless, but that she had searched the wrong berth and killed the wrong man; when she saw me emerge, unhurt, just as she was bracing herself for the discovery of my dead body, then she went into hysterics.  You remember, I gave her some whisky.

“It really seems a tenable theory.  But, like the Sullivan theory, there are one or two things that don’t agree with the rest.  For one thing, how did the remainder of that chain get into Alison West’s possession?”

“She may have picked it up on the floor.”

“We’ll admit that,” I said; “and I’m sure I hope so.  Then how did the murdered man’s pocket-book get into the sealskin bag?  And the dirk, how account for that, and the blood-stains?”

“Now what’s the use,” asked McKnight aggrievedly, “of my building up beautiful theories for you to pull down?  We’ll take it to Hotchkiss.  Maybe he can tell from the blood-stains if the murderer’s finger nails were square or pointed.”

“Hotchkiss is no fool,” I said warmly.  “Under all his theories there’s a good hard layer of common sense.  And we must remember, Rich, that neither of our theories includes the woman at Doctor Van Kirk’s hospital, that the charming picture you have just drawn does not account for Alison West’s connection with the case, or for the bits of telegram in the Sullivan fellow’s pajamas pocket.  You are like the man who put the clock together; you’ve got half of the works left over.”

“Oh, go home,” said McKnight disgustedly.  “I’m no Edgar Allan Poe.  What’s the use of coming here and asking me things if you’re so particular?”

With one of his quick changes of mood, he picked up his guitar.

“Listen to this,” he said.  “It is a Hawaiian song about a fat lady, oh, ignorant one! and how she fell off her mule.”

But for all the lightness of the words, the voice that followed me down the stairs was anything but cheery.

  “There was a Kanaka in Balu did dwell,
  Who had for his daughter a monstrous fat girl-

he sang in his clear tenor.  I paused on the lower floor and listened.  He had stopped singing as abruptly as he had begun.

CHAPTER XXII

AT THE BOARDING-HOUSE