A warm, clear night had been followed by a morning of drenching fog.  At about the middle of the afternoon of the preceding day a little whiff of light vapor—­a mere thickening of the atmosphere, the ghost of a cloud—­had been observed clinging to the western side of Mount St. Helena, away up along the barren altitudes near the summit.  It was so thin, so diaphanous, so like a fancy made visible, that one would have said:  “Look quickly! in a moment it will be gone.”

In a moment it was visibly larger and denser.  While with one edge it clung to the mountain, with the other it reached farther and farther out into the air above the lower slopes.  At the same time it extended itself to north and south, joining small patches of mist that appeared to come out of the mountainside on exactly the same level, with an intelligent design to be absorbed.  And so it grew and grew until the summit was shut out of view from the valley, and over the valley itself was an ever-extending canopy, opaque and gray.  At Calistoga, which lies near the head of the valley and the foot of the mountain, there were a starless night and a sunless morning.  The fog, sinking into the valley, had reached southward, swallowing up ranch after ranch, until it had blotted out the town of St. Helena, nine miles away.  The dust in the road was laid; trees were adrip with moisture; birds sat silent in their coverts; the morning light was wan and ghastly, with neither color nor fire.

Two men left the town of St. Helena at the first glimmer of dawn, and walked along the road northward up the valley toward Calistoga.  They carried guns on their shoulders, yet no one having knowledge of such matters could have mistaken them for hunters of bird or beast.  They were a deputy sheriff from Napa and a detective from San Francisco—­ Holker and Jaralson, respectively.  Their business was man-hunting.

“How far is it?” inquired Holker, as they strode along, their feet stirring white the dust beneath the damp surface of the road.

“The White Church?  Only a half mile farther,” the other answered.  “By the way,” he added, “it is neither white nor a church; it is an abandoned schoolhouse, gray with age and neglect.  Religious services were once held in it—­when it was white, and there is a graveyard that would delight a poet.  Can you guess why I sent for you, and told you to come heeled?”

“Oh, I never have bothered you about things of that kind.  I’ve always found you communicative when the time came.  But if I may hazard a guess, you want me to help you arrest one of the corpses in the graveyard.”

“You remember Branscom?” said Jaralson, treating his companion’s wit with the inattention that it deserved.

“The chap who cut his wife’s throat?  I ought; I wasted a week’s work on him and had my expenses for my trouble.  There is a reward of five hundred dollars, but none of us ever got a sight of him.  You don’t mean to say—­”