“I suppose it requires a lot of servants to keep a big house like that going.”
“He’s only got one now, sir: Milly Brown, who lives in Torquay. She is leaving on Saturday. The cook left last week. The doctor has all his meals at the hotel.”
He left Manfred to talk to the landlady—and Manfred could be very entertaining.
Slipping through the garden he reached a little alleyway at the back of the houses. The back gate giving admission to the doctor’s garden was locked, but the wall was not high. He expected that the door of the house would be fastened, and he was not surprised when he found it was locked. A window by the side of the door was, however, wide open: evidently neither the doctor nor his maid expected burglars. He climbed through the window on to the kitchen sink, through the kitchen and into the house, without difficulty. His search of the library into which he had been shown that afternoon was a short one. The desk had no secret drawers, and most of the papers had been burnt. The ashes overflowed the grate on to the tiled hearth. The little laboratory, which had evidently been a creamery when the house was in former occupation, yielded nothing, nor did any of the rooms.
He had not expected that in this one search he would make a discovery, remembering that the police had probably ransacked the house after the doctor’s arrest and had practically been in occupation ever since.
He went systematically and quickly through the pockets of all the doctor’s clothing that he found in the wardrobe of his bedroom, but it produced nothing more interesting than a theatre programme.
“I’m afraid I shan’t want that key,” said Leon regretfully, and went downstairs again. He turned on his pocket lamp: there might be other clothing hanging in the hall, but he found the rack was empty.
As he flashed the light around, the beam caught a large tin letter-box fastened to the door. He lifted up the yellow lid and at first saw nothing. The letter-box looked as if it had been homemade. It was, as he had seen at first, of grained and painted tin that had been shaped roughly round a wooden frame; he saw the supports at each corner. One was broken. He put in his hand, and saw that what he thought had been the broken ends of the frame, was a small square packet standing bolt upright: it was now so discoloured by dust that it seemed to be part of the original framework. He pulled it out, tearing the paper cover as he did so; it had been held in its place by the end of a nail which had been driven into the original wood, which explained why it had not fallen over when the door had been slammed. He blew the dust from it; the package was addressed from the Pasteur Laboratory. He had no desire to examine it there, and slipped it into his pocket, getting out of the house by the way he had come in, and rejoining Manfred just when that gentleman was beginning to get seriously worried, for Leon had been three hours in the house.
“Did you find anything?” asked Manfred when they were alone.
“This,” said Leon. He pulled the packet out of his pocket and explained where he had found it.
“The Pasteur Institute,” said Manfred in surprise. “Of course,” he said suddenly, “the serum which the doctor used to inject into his wife’s arm. Pasteur are the only people who prepare that. I remember reading as much in the account of the trial.”
“And which he injected twice a week, if I remember rightly,” said Leon, “on Wednesdays and Saturdays, and the evidence was that he did not inject it on the Wednesday before the murder. It struck me at the time as being rather curious that nobody asked him when he was in the witness box why he had omitted this injection.”
He cut along the paper and pulled it apart: inside was an oblong wooden box, about which was wrapped a letter. It bore the heading of the laboratory, directions, and was in French:
“Sir (it began),
“We despatch to you immediately the serum Number 47 which you desire, and we regret that through the fault of a subordinate, this was not sent you last week. We received your telegram today that you are entirely without serum, and we will endeavour to expedite the delivery of this.”
“Entirely without serum,” repeated Gonsalez. He took up the wrapping-paper and examined the stamp. “Paris, the 14th September,” he said, “and here’s the receiving stamp, Newton Abbot the 16th September, 7 a.m.”
He frowned.
“This was pushed through the letter-box on the morning of the 16th,” he said slowly. “Mrs. Twenden was injected on the evening of the 15th. The 16th was a Sunday, and there’s an early post. Don’t you see, Manfred?”
Manfred nodded.
“Obviously he could not have injected serum because he had none to inject, and this arrived when his wife was dying. It is, of course, untouched.”
He took out a tiny tube and tapped the seal.
“H’m,” said Leon, “I shall want that key after all. Do you remember, Manfred, he did not inject on Wednesday: why? because he had no serum. He was expecting the arrival of this, and it must have gone out of his mind. Probably we shall discover that the postman knocked, and getting no answer on the Sunday morning, pushed the little package through the letter-box, where by accident it must have fallen into the corner where I discovered it.”
He put down the paper and drew a long breath.
“And now I think I will get to work on that key,” he said.
Two days later Manfred came in with news.
“Where is my friend?”
Mrs. Martin, the landlady, smiled largely.
“The gentleman is working in the greenhouse, sir. I thought he was joking the other day when he asked if he could put
