How does O. Henry use suspense in "The Furnished Room"?
The story begins with descriptions of transients, homeless people, those who move from home to home out of economic necessity. This establishes a dark setting, stories about people who have no permanent homes. It is a description of countless nameless people, statistics really, and how they move through life "fugacious as time itself." Fugacious means "tending to disappear." The opening is quite bleak.
Then we have an unnamed man looking for a room. The maid who answers his knock reminds him of a worm. The dark, depressing descriptions add suspense to the story by giving a foreboding sense of what might happen.
The suspense is significantly increased when we learn that the man has been searching for someone he loves:
He was sure that since her disappearance from home this great, water-girt city held her somewhere, but it was like a monstrous quicksand, shifting its particles constantly, with no foundation, its upper granules of today buried tomorrow in ooze and slime.
The room the man finds himself in is filled with gloom, which O. Henry so poetically describes. All of this gloom combined with the saga of the man's ongoing, seemingly futile search adds to the suspense. The reader is left with bleak suppositions. If the man finds who he is looking for, will it be a tragic discovery? Given the bleak mood, setting, and situation, the suspense is heightened by the likelihood of something tragic to come.