He simply grinned at her. After a moment the angry light left her eyes.

"You've got to figure you're trapped on that car business," he told her. "You've got to switch around on that."

"But," she said, "that's going to bring Rob into it. If they know Rob was there, that's going to make an awful mess, because there was bad blood between Rob and my uncle."

"Did Rob see your uncle the night he was murdered?" asked Mason.

She shook her head, hesitated a moment, then nodded it.

"Yes," she said, "he did."

"And the reason you changed your story just now and admitted it," he said, "is that you suddenly remembered there is someone who knows Rob saw your uncle. Who is that someone—Don Graves?"

She nodded her head again.

Perry Mason stepped to the door of the outer office.

"Della," he said, "get me Doctor Prayton on the telephone right away. Tell his nurse that it's vitally important—a matter of life and death. Get him on the telephone personally, and do it now."

"Yes," she said. "There's a Mr. Paul Drake in the office who wants to see you about a personal matter. He won't tell me what it is."

"All right," snapped Perry Mason. "Tell him to wait," and he stepped back into the office, slamming the door.

"Now," he told the girl, "you're going to have a nervous breakdown. You'll be sent to a sanitarium under another name. The police will find you sooner or later. But I want it to be later. Don't let anyone know who you are, don't show any undue interest in the newspaper reports of the case, and, no matter what happens, don't get stampeded."

She stared at him searchingly.

"How do I know I can trust you?" she asked.

He met her gaze with a steady stare.

"That's one of the things you can use your own judgment about," he said, "and it's going to make a hell of a lot of difference what you do."

"All right," she told him, "I'm going to trust you."

He nodded.

"Under those circumstances," he said, "I'll order the ambulance right now before Doc Prayton gets here."

Paul Drake, the detective, bore no resemblance whatever to the popular conception of a private detective, which was, perhaps, why he was so successful.

He was a tall man, with a long neck that was thrust forward inquiringly. His eyes were protruding, and glassy, and held a perpetual expression of droll humor. Nothing ever fazed him. In his life, murders were everyday occurrences; love nests as common as automobiles, and hysterical clients merely part of an everyday routine.

He sat in the big highbacked leather chair in Perry Mason's office, and turned sideways, so that his long legs were crossed over the right hand arm of the chair. A cigarette was in his mouth, hanging pendulously at an angle from his lower lip.

Perry Mason, seated back of the big desk, stared at the detective with patient eyes that were calmly watchful. His manner was that of a veteran fighter relaxed in his corner, waiting for the sounding of the gong. He looked like a man who would presently lose his relaxed watchfulness, spring from the chair, and engage in swift conflict, with the ferocity of a tiger.

"Well," said Drake, "what's eating you?"

"Awhile back," said Perry Mason, "you were telling me something about a rough shadow."

Paul Drake inhaled placidly on his cigarette. His glassy, protruding eyes watched Perry Mason with an expression of quizzical humor.

"You must have a good memory," he said. "That was a long time ago."

"Never mind when it was," Mason told him. "I want to get the lowdown on it."

"Somebody trying it on you?" asked the detective.

"No," said Mason. "But I have an idea I can use it! Give me the sketch."

Paul Drake removed the cigarette from his mouth, pinched it out, and dropped it into an ashtray.

"It's a stunt in detective work," he said. "We don't ordinarily talk about it—not to outsiders, anyway. It's a psychological third degree. It's predicated on the idea that a man who has something on his mind that he's trying to conceal, is likely to be nervous."

"How does it work?" Mason asked tonelessly.

"Well, let's figure that you're working on a case, and you figure somebody has got some knowledge—not just ordinary knowledge, but a sort of guilty knowledge that he's trying to conceal. You've got two or three ways of approaching him in order to get him to spill the beans. One of them is to use the routine stunt of getting an attractive woman to get acquainted with him, and start him boasting. Another one is to plant some man who becomes friendly with him, and gets his confidence.

"Usually one of those ways works out. But sometimes they don't work. Sometimes a man won't fall for a woman, or, if he does, won't start boasting, and he'll get suspicious if one of your operatives starts getting friendly with him. That's when we use the rough shadow. It takes two men to work a rough shadow job. First, you have your contact man who makes a contact with the suspect, but can't seem to get under his hide, can't get him to talk.

"Well, you pick the time and a suitable place, and have your rough shadow trailing along behind. The contract man starts the fireworks by giving a signal.

"Of course, you understand, shadowing is a job in itself. The public gets goofy ideas about the work of a shadow, and how he operates. The public gets the idea that a shadow puts on disguises and ducks into doorways or hides behind telephone poles, and all that sort of stuff. They get that way from looking at the movies and reading a lot of detective stories written by guys that don't know anything about the detective business.

"As a matter of fact, your real shadow is a smooth guy who almost never uses a disguise. He's just a casual, innocentlooking bystander. No matter what happens, he never gets rattled and never does any of this business of ducking in a doorway. He looks so matteroffact that the suspect always takes him as part of the general scenery, and never thinks of him as an individual."

"I know all that, in a general way," Perry Mason told him. "What I want to get straight is just how this rough shadow game is worked."

"Well, that's simple," said the detective. "It's like all of the good things—they're simple when you come right down to analyze them. The rough shadow simply acts the way the suspect figures a shadow should act. In other words, he quits being a regular shadow, and becomes crude. He does all the things that the suspect naturally expects a detective would do. He hides behind telephone poles and ducks in doorways, and all of that stuff."

"So that the suspect knows he's being shadowed?" asked Perry Mason.

"That's the idea," said Drake, taking another cigarette from a case in his pocket, and tapping it gently on his thumb nail.

"You see, the contact man has established a certain amount of friendly relations with the suspect. The suspect, however, is a guy who won't talk about the thing that the contact man wants him to talk about, so the contact man gets a shadow to tail along behind. The suspect never knows that he's being tailed, because the shadow is a smooth worker. But, when the circumstances are right, the contact man gives a signal, and then the shadow gets crude about his methods. He starts ducking around behind telephone poles, putting on disguises, and doing the hundred and one amateurish things which defeat the very purpose of a skilled shadow. Naturally, the suspect takes a tumble that he's being tailed.

"Now, it's a funny thing about a man finding out that he's being shadowed, particularly a man who ain't used to it. As soon as he finds that somebody's tailing him around, he starts getting nervous. Usually the first thing he does is to start walking faster, and looking back over his shoulder. Naturally, the contact man has the rough shadow game sprung when he's walking with the suspect, and the contact man always slows down and saunters along.