When Karnes saw Brittain press the buzzer, he waited a second and took a chance. "Here," he said, fishing in his pocket, "I'll let you in." _That ought to give him the impression I live here._ Brittain smiled fetchingly. "Thanks, but I--" Bzzzz! The old-fashioned lock announced that it was open. Karnes stopped fishing and opened the door, letting Brittain follow him in. He stayed in the lead to the elevator, and pushed the button marked "4." "You getting off before four?" he asked conversationally. "No." The elevator slid on up to four without another word being said by either man. Karnes was judging the speed of the elevator, estimating the time it took for the doors to open as they did so, and making quick mental comparisons with his own ability to climb stairs at a run. The elevator was an old one, and fairly slow-- When the doors slid open, he stepped out and began to walk easily down the hall toward the stairway. When the elevator clicked shut, he broke into a run and hit the stairway at top speed, his long legs taking the steps three at a time. The stairway was poorly lit, since it was hardly ever used, and, at the fifth floor, he was able to conceal himself in the darkness as Brittain turned up the hall toward 523. Karnes looked closely at his surroundings for the first time. There was a well-worn, but not ragged, nylon carpet on the floor, dull chrome railing on the stair bannisters, and the halls were lit by old-fashioned glo-plates in the ceiling. The place was inexpensive, but not cheap. Having made sure that Brittain actually had entered 523, he stepped back toward the elevator in order to notify Lansberg. A sudden voice said: "You lookin' for-a somebody, meester?" Karnes turned. An elderly man with a heavy mustache and a heavy body stood partway up the stairs, clad in slacks and shirt. "Who are you?" frowned Karnes. "I'm Amati, the supratendent. Why?" The scowl was heavy. Karnes couldn't take any chances. The man might be perfectly okay, but-- * * * * * Lansberg's steps sounded, coming up the stairs. With him was a Manhattan Squad officer of the Police Department. "Shhh, Mr. Amati. C'mere a minute," said the cop. "Oh. Lootenant Carnotti. Whatsa--" "Shhhhhh! C'mere, I said, and be quiet!" "You know this man?" Lansberg asked the policeman softly, indicating Amati. "Sure. He's okay." Lansberg turned to the superintendent. "What do you know about the guy who just came in?" Amati seemed to have realized that something serious was going on, for his voice dropped to a conspiratorial whisper. "I dunno. I don't-a see who it is. Whatsa goin' on, Lootenant Carnotti?" "What about Apartment 523? Who lives there?" asked Karnes. "Oh, them? Meester and Meeses Seigert. Artists. Sheesa paint pictures, heesa make statues." Then Amati's eyes widened knowingly. "Ohhh! You guys da Vice Squad, eh? I _theenk_ theresa someteeng fonny about them!"