Mason fitted a latchkey to the exit door of his private office and entered, to find Della Street seated at her secretarial desk, telephoning. She said into the transmitter, “Okay, I’ll tell him. He’s coming in the door now,” hung up, smiled and said to Mason, “Well, your lame canary seems to have brought you a mystery after all.”

“I’ll say. Who was on the line?”

“Drake’s secretary. She said to tell you operatives hadn’t been able to contact Jimmy Driscoll, Rita Swaine, or Rosalind Prescott. And, of course, the police are looking for all three, so they must have skipped out.”

“All right,” Mason said, “what did she tell you about the murder?”

“Nothing new. Prescott was found in the upstairs bedroom, shot three times with a .38 caliber revolver. The revolver the police found, where Rita Swaine had hidden it, was also a .38. Drake’s men haven’t been able to find out whether the rifling marks on the bullets are identical. The probabilities are the police haven’t the information themselves yet. Tell me, Chief, if Rita had been mixed up in the killing, why didn’t she say so frankly when she came in here? She must have known it would all come out. Having you working in the dark didn’t help her any.”

Mason crossed the room, sat on the corner of his desk and lit a cigarette. “Do you know what Paul Drake’s men have discovered, Della?”

She nodded. “I was talking with Mabel Foss a few minutes ago. She gave me the latest.”

“Then you’ve probably noticed that the only evidence which connects Rita Swaine with the actual murder is the testimony of Stella Anderson.”

“Otherwise known as ‘Mrs. Snoops,’ ” Della Street commented. “What about her?”

“It isn’t about her,” Mason said slowly, “it’s about the evidence, Della. She says that Rita Swaine was clipping the canary’s claws, that there was a passionate love scene between her and Jimmy Driscoll, that the canary escaped. And about that time there was this automobile accident. Jimmy ran out and helped load the victim into the van which took him to the hospital. Then Jimmy came back and gave Rita a gun which Rita hid. Then, as he was leaving the house, Jimmy ran right smack into the arms of the officers. Thereafter an interval elapsed during which the witness couldn’t see what was going on in the house. Later on she saw Rita return, catch the canary, and finish trimming its claws. Now then, notice that, on this occasion Rita apparently needed plenty of light to determine what she was doing. Before, she’d been able to clip the canary’s claws standing near the middle of the solarium, and without bothering to move the lace curtains. But when she finished the job, she found it necessary not only to come to the window, but to push aside the curtain and stand directly against the window, clipping the claws on the canary’s right foot.”

“But,” Della Street said, frowning, “isn’t that the foot that’s clipped too closely?”

Mason nodded.

“Well,” she said, “go ahead, Chief, tell me the rest of it.”

“At the time,” Mason went on, “Rita was wearing one of Rosalind’s dresses. Does that mean anything to you?”

Della Street shook her head, “Not a dam thing, Chief, except that I always felt I was short-changed by not having any sisters. Two sisters who are the same height and build can— Hey, wait a minute! You don’t mean—” Her voice trailed away into silence as she stared at the lawyer with wide-open, startled eyes.

“That’s exactly what I mean,” Mason said, “Mrs. Snoops was standing in her window, looking in the solarium. She saw the frenzied love scene, and she saw Jimmy Driscoll hand Rosalind Prescott the gun. At the time, Rosalind and Jimmy were too engrossed in what they were doing to pay very much attention to their surroundings. Later on, Rosalind saw Mrs. Snoops standing outlined against the window, and realized she’d seen everything.

“Now, let’s analyze that situation a bit: Rosalind was standing in the solarium in front of the desk, which is some eight or ten feet back from the windows. The windows are covered with thin lace curtains. It’s possible to see through those curtains and into the solarium, but not too distinctly. On the other hand, Rosalind, standing there near the center of the room, looking out through those curtains, and across to the Anderson house could very plainly see the angular form of Stella Anderson standing at the window, very apparently an interested observer of what had been taking place.”

“Then,” Della Street said positively, “it was Rosalind Prescott Jimmy made love to and not Rita Swaine.”

Mason said cautiously, “It looks like it.”

“And was Rita in the house at the time?”

“Probably not,” Mason said. “Remember that later on, when Rita appeared at the window with the canary, she was wearing one of Rosalind’s dresses. It was a print dress with a distinctive flower design, striking enough in pattern and vivid enough in color so Stella Anderson could easily recognize it. She was more certain of the identity of the dress than of the person wearing it when she’d seen it earlier.

“Now then, let’s suppose that sometime around noon Rita Swaine was summoned to the telephone, and heard the frantic voice of her sister saying, ‘Listen, Rita, I’m in an awful jam. Jimmy Driscoll was over here and we just couldn’t keep apart. He took me in his arms and I forgot everything and clung to him. Then I looked up, and who should we see watching us but old Mrs. Snoops. Now, you know what that means. Walter’s going to sue me for divorce, and drag Jimmy into it if he can. We just can’t let Mrs. Snoops testify that Jimmy was in the house, making love to me, while Walter was at the office.’

“Then it’s possible Rita said, ‘Well, lie out of it. Pretend that Jimmy’s your brother. After all, she doesn’t know who Jimmy is,’ and Rosalind said, ‘We can’t do that because there was an automobile accident, and when Jimmy went to leave the house, the officers took his name and address from his driving license, so we’re up against it. Now listen, Rita, I was clipping the canary’s claws at the time. The canary got away and is still flying around the solarium. Jimmy has left, and I’m going to Reno. Now suppose you come over and put on that print dress of mine, which is the one I was wearing, catch the canary, go back over and stand in front of the window, as though you’d come back to finish clipping his claws. Make certain Mrs. Snoops sees you. When you see her looking, pull the curtain aside so she can get a good look. Then she’ll see that it’s you instead of me. That’ll make her think it was you all along. Then you can announce to some of your intimate friends that Jimmy’s madly in love with you, but you don’t want me to know it right at present. Do it in such a way it gets back to Mrs. Snoops.’ ”

“Do you mean to say she’d let her sister in for that?” Della Street asked. “With Walter Prescott’s body lying upstairs all the time?”

Mason shook his head and said, “That’s exactly it, Della, I don’t think she’d have done it if she’d known Walter’s body was upstairs in the bedroom.”

“But she must have known it if she went up there to pack her things.”

“She didn’t pack. She left that for Rita to do. And the body was in Walter’s bedroom, not hers.”

“Well, after Rita came to the house, then what happened?”

“That,” Mason said, “is something else. Of course, Rita might or might not have gone into Walter’s bedroom. Rosalind would have left the dress in her bedroom. Rita could have gone there and changed, then gone down and clipped the claws on the canary. Naturally, she was thinking more of registering with Mrs. Snoops than of what she was doing, so she clipped the right foot twice, without noticing that the right foot had been finished, while the left foot hadn’t.”

“One thing, Chief,” Della Street said, as she stared at him through thought-slitted eyes: “Why do you say Rosalind Prescott said, ‘I’m going to Reno’?”

Mason grinned and said, “That’s a break. I went down to talk with Karl Helmold about the canary. Rita Swaine had told him I sent her, but she’d given him the name of Mildred Owens and the address as General Delivery, Reno. You see, Della, she intended to leave the canary there temporarily, but to send for him later on. Perhaps she knew that her name was going to be in the papers. Perhaps she’d already picked the alias of Mildred Owens and wanted to have it so the canary could be sent to her under her alias without any trouble, and whenever she wrote for it.”

Della Street, staring at him, said, “And that means you’re going to Reno?”

He nodded. “We’re going.”

“Going to try to beat the cops to it?”

Again he nodded, “And it may be dangerous, Della. We’re playing with legal dynamite.”

She scooped up a notebook, pencils, and said, “Okay. Let’s go.”

Mason helped her into her coat. “Naturally,” he said, “it’s important as the devil no one knows where we’re going nor why we’re going. We’ll charter a special plane at the airport. Now, there’s just a chance Sergeant Holcomb may start looking for me, find me gone, put two and two together, and take a chance on calling the airport. So you ring up and engage the plane under your name.”

“Why not use an assumed name?”

“Because,” he told her, “I don’t want to do anything which would show a guilty intent. This is plenty warm right now. Before we get done with it, it’s going to be hot. I don’t want you to get your fingers burnt.”

“Never mind my fingers,” she told him, “but you keep in the clear, Chief. Remember, you’re going to take a cruise around the world.”

He nodded and said, “It’ll be fun, Della, but I’ll miss the action of a rough-and-tumble law business, at that.”

“Don’t worry,” she told him, “you’ll have plenty of action — dances on the deck in the moonlight, the beach at Waikiki, Japan in Cherry Blossom Time, across the Yellow Sea, up the Whang Poo to Shanghai, the Paris of the Orient, with—”

“You,” he charged, leveling an accusing forefinger at her, “have been reading steamship literature.”

“And how!” she admitted. “In case you want to know, Chief, I took all the papers out of your top drawer and loaded it up with pamphlets on Bali, the Orient, Honolulu, India, and—”

He circled her waist with his arm, swept her off her feet and around in a circle toward the door. “Come on, baggage,” he told her, “there’s work to be done.”