"I know how Ken Mallory did it!" Her voice was charged with excitement. "There was trichloroethylene in Kat's body."

"Inspector, Dr. Taylor is here to see you."

"Again?" He was tempted to turn her away. She was obsessed with the half-baked theory she had. He was going to have to put a stop to it. "Send her in."

When Paige walked into his office, Inspector Burns said, "Look, doctor, I think this has gone far enough. Dr. Dolan called to complain about --"

He nodded. "Dr. Dolan told me that. But he said it couldn't have made her unconscious. He --"

"Chloral hydrate turns into trichloroethylene!" Paige said triumphantly. "Mallory lied when he said he didn't go back into the apartment with Kat. He put chloral hydrate in her drink. It has no taste when you mix it with alcohol, and it only takes a few minutes for it to work. Then when she was unconscious, he killed her and made it look like a bungled abortion."

"No, it isn't. He wrote the prescription for a patient named Spyros Levathes, but he never gave it to him."

"Doctor, if you'll forgive my saying so, that's a hell of a lot of speculation."

His fingers were drumming on his desk. "It's not that simple."

"What's that?"

Inspector Burns raised a hand. "All right. I'll tell you what I'll do. I'll talk to the district attorney's office and see whether they think we have a case."

For the first time, Inspector Burns was impressed. "You've really done your homework, haven't you?"

"Dr. Mallory didn't give his patient chloral hydrate because it would have killed him! Chloral hydrate is contraindicated for porphyria. It would have caused immediate convulsive seizures."

"Because he couldn't have. I checked on Spyros Levathes. He has erythropoietic porphyria."

"I still don't understand."

"It's a genetic metabolic disorder. It causes photosensitivity and lesions, hypertension, tachycardia, and a few other unpleasant symptoms. It's the result of a defective gene."

"You've got to…"

"How do you know that?"

Paige pressed on. "Why would Ken Mallory go to a remote pharmacy and fill a prescription for a patient he knew he couldn't give it to? You've got to arrest him."

Then there was the matter of the chloral hydrate. Mallory had written a prescription for a drug that could have killed his patient. Was he guilty of murder? Not guilty?

"I'll get back to you."

Paige knew she had gone as far as she could. "Thank you, inspector."

After Paige Taylor left, Inspector Burns sat there thinking about their conversation. There was no hard evidence against Dr. Mallory, only the suspicions of a persistent woman. He reviewed the few facts that he had. Dr. Mallory had been engaged to Kat Hunter. Two days after she died, he was engaged to Alex Harrison's daughter. Interesting, but not against the law.

Mallory had said that he dropped Dr. Hunter off at her front door and did not go into the apartment. Semen was found in her body, but he had a plausible explanation for that.

Burns buzzed his secretary on the intercom. "Barbara, get me an appointment with the district attorney this afternoon."

There were four men in the office when Paige walked in: the district attorney, his assistant, a man named Warren, and Inspector Burns.

"But why?"

"Doctor, in a court of justice, ignorance of the law is no excuse. But ignorance in medicine is."

"I'm afraid we can't do that."

"We can't arrest Dr. Mallory."

"We have no case."

"Of course you have!" Paige exclaimed. "The trichloroethylene proves that --"

So they're going to arrest Ken Mallory after all!

"Thank you for stopping by, Dr. Taylor," the district attorney said. "Inspector Burns has been telling me of your interest in the death of Dr. Hunter. I can appreciate that. Dr. Hunter was your roommate, and you want to see justice done."

"I don't understand."

"It's simple. It means that Dr. Mallory could claim he made a mistake, that he didn't know what effect chloral hydrate would have on a patient with porphyria. No one could prove he was lying. It might prove that he's a lousy doctor, but it wouldn't prove that he's guilty of murder."

"Yes," Paige said. "There's no doubt about it. Dr. Mallory killed her. When you arrest him, he --"

Paige looked at him in frustration. "You're going to let him get away with this?"

Paige looked at him blankly. "What?"

He studied her a moment. "I'll tell you what I'm prepared to do. I've discussed this with Inspector Burns. With your permission, we're going to send someone to your apartment to pick up the glasses in the bar. If we find any traces of chloral hydrate, well take the next step."

"And there were fingerprints on that glass. We're going to check them against Dr. Mallory's prints."

Paige felt a surge of excitement.

"What if he rinsed them out?"

Paige closed her eyes in a silent prayer of thanks.

"We found one with traces of chloral hydrate."

The inspector went on, "When he killed her -- if he did kill her -- he was wearing gloves, so his fingerprints wouldn't be on the curette. But he couldn't very well have served her a drink while he wore gloves, and he might not have worn them when he put the glass back on the shelf after rinsing it out."

Two hours later, Inspector Burns was on the phone with Paige.

Paige steeled herself for disappointment.

"We did a chemical analysis of all the glasses in the bar, doctor," Burns said.

Inspector Burns said dryly, "I don't imagine he took the time to use a detergent. If he just rinsed out the glasses, we'll find what we're looking for."

Mallory laughed. "You don't have to worry about that, baby. There isn't anyone in the world for me but you."

Ken Mallory was listening to Lauren on the telephone. "Father and I found some office space that you're going to adore, darling! It's a beautiful suite in the 490 Post Building. I'm going to hire a receptionist for you, someone not too pretty."

"I have to admit that in the beginning, I didn't believe your theory was going anywhere. I think now maybe Dr. Mallory could be our man. But proving it is going to be another matter." He continued, "The district attorney is right. It would be a tricky business to bring Mallory to trial. He can still say that the prescription was for his patient. There's no law against making a medical mistake. I don't see how we --"

"Wait a minute!" Paige said excitedly. "I think I know how!"

"No," Paige said. "He couldn't, could he?"

"I'm dying for you to come see it. Can you get away now?"

"Wonderful! Why don't you pick me up at the house?"

"I'm off in a couple of hours."

"All right. I'll be there." Mallory replaced the telephone. It doesn't get any better than this, he thought. There is a God, and She loves me.

They stepped inside. There were three people in the room -- a man in bed, a male nurse, and a doctor Mallory had not met before.

He heard his name called over the PA system: "Dr. Mallory… Room 430… Dr. Mallory… Room 430." He sat there daydreaming, thinking about the golden future that lay ahead of him. A beautiful suite in the 490 Post Building, filled with rich old ladies eager to throw their money at him. He heard his name called again. "Dr. Mallory… Room 430." He sighed and got to his feet. I'll be out of this goddam madhouse soon, he thought. He headed toward Room 430.

A resident was waiting for him in the corridor, outside the room. "I'm afraid we have a problem here," he said. "This is one of Dr. Peterson's patients, but Dr. Peterson isn't here. I'm having an argument with one of the other doctors."

The resident said, "This is Dr. Edwards. We need your advice, Dr. Mallory."

The resident explained. "This patient is suffering from erythropoietic porphyria, and Dr. Edwards insists on giving him a sedative."

"I don't see any problem with that."

"What's the problem?"

Mallory was looking at him in astonishment. "Are you out of your mind? That could kill him! He'd have a convulsive seizure, tachycardia, and he'd probably die. Where in hell did you study medicine?"

"Thank you," Dr. Edwards said. "The man hasn't slept in forty-eight hours. I've prescribed chloral hydrate for him so he can get some rest and…"

The man looked at Mallory and said quietly, "I didn't." He flashed a badge. "I'm with the San Francisco Police Department, Homicide." He turned to the man in bed. "Did you get that?"

Mallory was looking from one to the other, frowning. "I don't understand. What is this? What's going on?"

The man pulled out a tape recorder from under the pillow. "I got it."

The inspector turned to Mallory. "Dr. Mallory, you're under arrest for the murder of Dr. Kate Hunter."