It was just before Mason was closing the office that Dr. Alton telephoned.

«Is it all right if I come up for just a few minutes?» Dr. Alton asked. «I've had a terrific work load this afternoon with an office full of patients and I'm just this minute getting free.»

«I'll wait,» Mason said.

«I'll be there within ten minutes,» Dr. Alton promised.

Mason hung up the phone, turned to Della Street, «Any particular plans for this evening, Della? Can you wait with me for Dr. Alton?»

«I'll be glad to,» she said.

«After that,» Mason told her, «we can go out for dinner.»

«Now, those words are music to a secretary's ears,» she told him, «but may I remind you, you don't as yet have any retainer in this case which would cover expenses.»

«We're casting bread on the waters,» Mason said, «and don't let the matter of expense cramp your style. Just don't look at the right side of the menu.»

«My figure,» she sighed.

«Perfect,» Mason said.

She smiled. «I'll go out in the outer office and wait for Dr. Alton.»

«Bring him right in, as soon as he comes,» Mason told her.

Della Street went to the outer office and a few minutes later returned, opening the door and saying, «Dr. Ferris Alton.»

Dr. Alton came bustling forward, radiating intense nervous energy.

He grasped Mason's hand, said, «I'm very pleased indeed to meet you, Mr. Mason. I have to discuss this case with you, personally, which is the reason I'm bothering you.

«Incidentally, I have here two sterile phials containing the material you wanted, some clippings from the fingernails and some hair that has been pulled out by the roots.

«Now, I can either have this processed or you can.»

«Better let me do it,» Mason said. «It will attract less attention that way, and I have some connections which will give me a report within a very short time.»

«Well, I'd be very glad to have you do it,» Dr. Alton said, «but now that you've planted the suspicion in my mind, I have an uneasy feeling that we're going to have positive reactions; that there will be at least two areas in the hair that will show arsenic.

«The first attack took place approximately seven and a half months ago-too long a time, I'd guess, for any traces of the poison to remain. But the second was five weeks ago, and the last one about a week ago.»

«Did you get a dietary history?» Mason asked.

«I wasn't utterly naive,» Dr. Alton said. «I wanted to find out if this was the result of an allergy or, as I suspected, contaminated food.

«On all occasions, she had eaten Mexican food.»

«Who cooked it?» Mason asked.

«She has a chauffeur, a George Eagan, who has been with her for some time. She is very much attached to him-in a business way, of course. He is young enough-Well, I believe there's quite a discrepancy in ages… oh, say fifteen years or so.

«He drives her everyplace and he is the one in charge of the outdoor cooking; whenever they have a barbecue, he does the steaks and the potatoes, does the cooking and the serving, toasts the French bread and all the rest of it. I gather he's very expert.

«He's also expert in cooking; the Mexican foods I mentioned are cooked out of doors.»

«Wait a minute,» Mason said, «she would hardly have the Mexican food cooked just for herself. There must have been others present.»

Dr. Alton said, «In getting a case history, I wasn't even suspicious of poisoning. Therefore, I asked only about what my patient had been eating. I didn't ask about others. I believe other relatives were also present. Eagan, the chauffeur, did the cooking. Apparently no one else besides Lauretta Trent had any symptoms.»

«I see,» Mason said.

«If it was poisoning, and I am now satisfied it was, it was done very expertly… Now then, Mr. Mason, I have a responsibility to my patient. I want to keep from having any recurrence.»

«I told you what to do,» Mason said sharply. «Get three nurses, put them on the job around the clock.»

Dr. Alton shook his head. «I am afraid that won't work.»

«Why not?» Mason asked.

Dr. Alton said, «We're not dealing with a child, Mr. Mason. We're dealing with a mature woman who likes to have her own way; who is rather arbitrary and-damn it, I've got to have some sort of an excuse to put out special dishes for her.»

Mason's mouth tightened. «How many nurses are on the job now?»

«Just one… a nurse she has from time to time.»

«And how did you get the fingernails and the hair?»

Dr. Alton said, uncomfortably, «I had to use a little subterfuge. I rang up the nurse and told her that I was going to give Mrs. Trent some medicine which might cause a temporary itching of the skin; that it was highly important that she not do any scratching and that I would like to have her nails trimmed down; that I wished she'd explain to the patient what I had in mind and what I was trying to accomplish. I also told her that I'd like to test the hair to see whether her digestive upsets had been due to an allergy caused by either a shampoo or a hair dye. I explained to the nurse that I didn't want to suggest that Mrs. Trent was coloring her hair; but that I felt there might be an allergy, particularly if she had had any itching or sore spots in her scalp and had scratched and had thereby caused an abrasion in the skin that would enable the dye materials to penetrate the bloodstream. I told the nurse to put the nail clippings and the hair in sterile phials.»

Mason said, «Nurses take courses in poisons and their treatment. Do you think your nurse suspected anything?»

«Oh no, not a thing,» Dr. Alton said. «I told the nurse I'd been puzzled about Mrs. Trent's case; that I couldn't believe that the disturbance resulted entirely from food poisoning but that I thought perhaps it might be a combination of things.»

«She didn't give any indication that she thought your requests were unusual?» Mason asked.

«None whatever. She accepted them just as any good nurse would, without any comment. I told her to get a taxi and send the nail parings and the hair in their sterile phials to my office at once.»

Mason said, «I know a laboratory which specializes in forensic medicine and toxicology that will give us a quick report on these, not a quantitative analysis, but it will show whether any arsenic is present.»

«How soon can you have that?»

Mason said, «I think I can have it right after dinner, Doctor.»

«I wish you'd telephone me,» Dr. Alton said.

«All right,» Mason told him, «but what have you done about furnishing your patient with round-the-clock protection?»

Dr. Alton's eyes shifted. «All right, Mason,» he said, «I'll put it right on the line. You almost convinced me when you talked over the telephone, and then I became more convinced when I thought over the symptoms. But when I took time to think things over, I felt I couldn't justify taking really drastic steps pending a laboratory report; but I have taken precautionary steps which will be ample for the time being.»

«What steps?» Mason asked, his voice coldly disapproving.

«I've decided that during the next few hours there won't be any element of real danger, particularly in view of the fact that this nurse, Anna Fritch, is on the job. However, I told her to see that Mrs. Trent was on a very bland diet tonight; that I intended to perform some tests and I wanted her to have nothing except soft boiled eggs and toast tonight; that I wanted the nurse to prepare both the eggs and the toast, and see that the eggs were served in the shell so that there would be no chance of too many spices being added.»

«All right,» Mason said, «if that's what you've done, that's what you've done. Give me your night number. I'll drop these things at the laboratory and ask for an immediate check… Now, what do you propose to do if the tests are positive and show the presence of arsenic?»