The Sinful Ones by Fritz Leiber

door to the stairs.
    Yet the “Herbert Gregg” apartment ought to be the one in which he had seen the old man sitting.
    Beyond the inner door, in the darkness of the stair well, he thought he saw something move. He couldn’t tell what it was. When he stepped closer and peered in, he saw nothing. He went outside. He craned his neck. The man was still sitting there. An old man—perhaps deaf?
    Then, as Carr watched, the man put down his paper, settled back, looked across the room, and from the window came the opening triplets of the first movement of the Moonlight Sonata.
    Carr felt the wire that fenced the tiny, nearly grassless plot press his calf and realized that he had taken a backward step. He reminded himself that he’d only heard Jane play the third movement. He couldn’t know she’d play the first just this way.
    He went back into the vestibule, again pushed the button.
    There was no faltering of the piano notes. They sounded icy, remove, inhuman, as if some huge insect were treading neatly, courtseyingly, infallibly up and down the keyboard.
    Carr again peered through the inner door. Light trickled down from the second landing above. He tried the door. Someone must have left it off the buzzer, for it opened.
    He hurried past the blackness of the bottom of the stair well. Five steps, a turn, five steps more. Then, just as he reached the first landing, which still wasn’t very light, he felt something small and silent come brushing up against his ankle from behind.
    His back and hands pressed to the plaster wall.
    Then he relaxed. Just a cat. A black cat with a white throat and chest, like evening clothes.
    And a very cool cat too. It walked suavely toward the door of the Gregg apartment.
    But about two feet away it stopped. For several seconds it stood there, head upraised, making no movement, except its fur seemed to thicken a little. Then, very slowly, it looked around.
    It stared at Carr.
    Beyond the door, the piano started the sprightly second movement.
    Carr edged out his hand. His throat felt dry and constricted. “Kitty,” he croaked.
    The cat arched its back, spat, then made a twisting leap that carried it halfway up the next semi-flight of stairs. It crouched on the top step, its bugged green eyes peering between the rails of the banister.
    There were footsteps. Without thinking, Carr shrank back. The door opened, the music suddenly swelled, and a gray-haired lady in a blue and white print dress looked out and called, “Gigolo! Here, Gigolo!”
    She had Jane’s small chin and short straight nose, behind veils of plumpness. Not Jane’s height, thought. She was rather dumpy. Her face had a foolish look.
    And she must be short-sighted, for although she looked at the stairs, she didn’t see the cat, nor did she notice Carr. Feeling uncomfortably like a prowler, he started to step forward, then realized that she was so close he would give her a fright.
    “Gigolo!” she called again. Then, to herself, “That cat!” A glance toward the dead bulb in the ceiling and a distracted headshake. “Gigolo!”
    She backed inside. “I’m leaving it open, Gigolo,” she called. “Come in when you want to.”
    Carr stepped out of the darkness with a husky, “Excuse me,” but the opening notes of the fast third movement, played too loudly, drowned him out.
    He crossed to the door. The green eyes at the top of the stairs followed him. He raised his hand to knock. But at the same time he looked through the half-opened door, across a tiny hall, into the living room.
    It was a smallish room, with too much heavy furniture in addition to the fake fireplace, and too many lace runners on little tables and antimacassars on the head rests and arms of chairs. He could see the other end of the red davenport and the slippered feet of the old man sitting in it. The woman had retired to a straight-backed chair across the room and was sitting with her hands folded, her lips worriedly pursed.
    Between them was the piano, an