During the day he had examined the setting for the night’s adventure.  He had been to the Denmark Building and scanned it inside and out.  He had gone up to the fourth floor and looked at the exterior of Room 419.  The office door had printed on it this design: 

  THE GOLD HILL MILLING & MINING COMPANY

But when Kirby tried the door he found it locked.

The Denmark Building is a little out of the heart of the Denver business district.  It was built far uptown at a time when real estate was booming.  Adjoining it is the Rockford Building.  The two dominate a neighborhood of squat two-story stores and rooming-houses.  In dull seasons the offices in the two big landmarks are not always filled with tenants.

The elevators in the Denmark had ceased running hours since.  Kirby took the narrow stairs which wound round the elevator shaft.  He trod the iron treads very slowly, very softly.  He had no wish to advertise his presence.  If there was to be any explosive surprise, he did not want to be at the receiving end of it.

He reached the second story, crossed the landing, and began the next flight.  The place was dark as a midnight pit.  At the third floor its blackness was relieved slightly by a ray of light from a transom far down the corridor.

Kirby waited to listen.  He heard no faintest sound to break the stillness.  Again his foot found the lowest tread and he crept upward.  In the daytime he had laughed at the caution which had led him to borrow a weapon from an acquaintance at the stockyards.  But now every sense shouted danger.  He would not go back, but each forward step was taken with infinite care.

And his care availed him nothing.  A lifted foot struck an empty soap box with a clatter to wake the seven sleepers.  Instantly he knew it had been put there for him to stumble over.  A strong searchlight flooded the stairs and focused on him.  He caught a momentary glimpse of a featureless face standing out above the light—­a face that was nothing but a red bandanna handkerchief with slits in it for eyes—­and of a pair of feet below at the top of the stairway.

The searchlight winked out.  There was a flash of lightning and a crash of thunder.  A second time the pocket flash found Kirby.  It found him crouched low and reaching for the .45 under his arm.  The booming of the revolver above reverberated down the pit of the stairway.

Arrow-swift, with the lithe ease of a wild thing from the forest, Kirby ducked round the corner for safety.  He did not wait there, but took the stairs down three at a stride.  Not till he had reached the ground floor did he stop to listen for the pursuit.

No sound of following footsteps came to him.  By some miracle of good luck he had escaped the ambush.  It was characteristic of him that he did not fly wildly into the night.  His brain functioned normally, coolly.  Whoever it was had led him into the trap had lost his chance.  Kirby reasoned that the assassin’s mind would be bent on making his own safe escape before the police arrived.