“He could cast a sight-avoidance spell on the mirror, couldn’t he?” Lord Bontriomphe asked. “That’s a static spell, I believe.”

“Certainly,” said Master Sean. “He could cast a sight-avoidance spell on every reflecting surface in the place. But a man has to look somewhere, and even a layman would get suspicious under circumstances like that. Besides, to anyone with even a half-trained Talent, he’d be detectable immediately.

“And even supposing he did make himself invisible outside that window, do you realize what he would have to do? Now you have him juggling three spells at once: he’s levitating himself; he’s making himself ‘invisible’; and he’s closing that window.

“No, my lord; it won’t do. It just isn’t humanly possible.”

Lord Darcy let his gaze wander over the room. “That’s settled, then. Our killer did not go out those windows either by thaumaturgical or by ordinary physical means. Therefore, we—”

“Wait a minute!” said Lord Bontriomphe, his eyes widening. He pointed a finger at Master Sean. “Look here; suppose it happened this way. The killer stabs Master Sir James. His victim screams. The killer knows that you are outside the door. He knows he can’t get out through the door. The windows are out, too, for the reasons you’ve just given. What can he do? He uses the Tarnhelm Effect. When I come busting in here with an ax, I don’t see him. As far as I’m concerned, the room is empty except for the corpse. I wouldn’t be able to see him, would I? Then, when the door’s open, he walks out as cool as an oyster, with nobody noticing him.”

Master Sean shook his head. “You wouldn’t notice him; that’s so. But I would have. And so would Grand Master Sir Lyon. We were both looking in through that hole in the door, and a man can see the whole room from there — even the bathroom, when the door to it is open.”

Lord Bontriomphe looked at the bathroom through the open door. “No, you can’t. Take a look. Suppose he were lying down in the tub. You couldn’t even see him from in here.”

“True. But I distinctly recall your looking down directly into the tub. You couldn’t have done that if a killer using the Tarnhelm Effect were in it.”

Lord Bontriomphe frowned thoughtfully. “Yes. I did. Hm-m-m. Well, that eliminates that. He wasn’t in the room, and he didn’t leave the room.” He looked at Lord Darcy. “What does that leave?”

“We don’t know yet, my dear fellow. We need more data.” He stepped over to where the body lay and knelt down, being careful not to disturb anything.

Master Sir James Zwinge had been a short, lean man, with receding gray hair and a small gray beard and moustache. He was wearing a neat, fairly expensive gentleman’s suit, rather than the formal sorcerer’s costume to which he was entitled. As Bontriomphe had said, it was difficult to see the stab wound at first glance. It was small, barely an inch long, and had not opened widely. It was further obscured by the blood which covered the front of the dead magician’s clothing. Nearby, a black-handled, silver-bladed knife lay in the pool of blood on the floor, its gleaming blade splashed with red.

“This blood—” Lord Darcy gestured with his hand. “Are you absolutely certain, Bontriomphe, that it was fresh when you broke into this room?”

“Absolutely certain,” Bontriomphe said. “It was bright red and still liquid. There was still a slight flow of blood from the wound itself. I’ll admit I am not a chirurgeon, but I am certainly no amateur when it comes to knowing something about that particular subject. He couldn’t have been dead more than a few minutes when I first saw his body.”

Lord Darcy nodded. “Indeed. The condition of the blood even now, under the preservation spell, shows a certain freshness.”

He gestured toward a key that lay a few feet away from the body. “Is that your key, my lord?”

Lord Bontriomphe nodded. “Yes. I put it there to mark the spot when I picked up Sir James’ key.”

“It is still where you put it?”

“Yes.”

Lord Darcy measured the distance between the key and the door with his eye. “Four and a half feet,” he murmured. He stood up. “Give me Sir James’ key. Thank you. An experiment is in order.”

“An experiment, my lord?” Master Sean repeated. His face brightened.

“Not of the thaumaturgical variety, my good Sean. That will come in good time.” He walked over to the door and opened it, ignoring the two Armsmen who stood at attention outside. He looked down at his feet. “Master Sean, would you be so good as to remove this brazier?”

The tubby little Irish sorcerer bent over and put his hand near the brazen bowl. “It’s still a little hot. I’ll put it on the table.” He picked up the tripod by one leg and carried it into the room.

“I don’t see what you’re getting at,” said Lord Bontriomphe.

“Surely you have noticed the clearance between the bottom of the door and the floor?” Lord Darcy said. “Is it possible that the murderer simply stabbed Sir James, came out, locked the door behind him, and slid the key back under the door?”

Master Sean blinked. “With me standing outside the door all the time?” he said in surprise. “Why, that’s impossible, me lord!”

“Once we have eliminated the impossible,” Lord Darcy said calmly, “we shall be able to concentrate on the merely improbable.”

He knelt down and looked at the floor beneath the door. “As you see, the space is somewhat wider than it appears to be from the inside. The carpeting does not extend under the door. Close the door, if you will, Master Sean.”

The sorcerer pushed the door shut and waited patiently on the other side. Lord Darcy put the heavy brass key on the floor and attempted to push it under the door. “I thought not,” he said, almost to himself. “The key is much too large and thick. It can be forced under—” He pushed hard at the key. “But it wedges tight. And the thickness of the carpet would stop it on the other side.” He pulled the key out. “Open the door again, Master Sean.”

The door swung inward. “Observe,” Lord Darcy continued, “how the attempt to push it under has scored the wood at that point. It would be impossible even to make the attempt without leaving traces, much less—” He paused, cutting off his own words abruptly. “What is this?” he said, leaning over to peer more closely at a spot on the carpet inside the room.

“What’s what?” asked Lord Bontriomphe.

Lord Darcy ignored him. He was looking at a spot on the carpet near the right-hand doorpost, on the side away from the hinges, and approximately eight inches in from the edge of the carpet itself.

“May I borrow your magnifying glass, Master Sean?” Lord Darcy said without looking up.

“Certainly.” Master Sean went over to the table, opened his symbol-decorated carpetbag, took out a large bone-handled lens, and handed it to his lordship.

“What is it?” he asked, echoing Lord Bontriomphe’s question. He knelt down to look, as Lord Darcy continued to study a small spot on the carpet without answering.

The mark, Master Sean saw, was a dark stain in the shape of a half circle, with the straight side running parallel to the door and the arc curving in toward the interior of the room. It was small, about half the size of a man’s thumbnail.

“Is it blood?” asked Master Sean.

“It is difficult to tell on this dark green carpet,” said Lord Darcy. “It might be blood; it might be some other dark substance. Whatever it is, it has soaked into the fibers of the pile, although not down to the backing. Interesting.” He stood up.

“May I?” said Lord Bontriomphe, holding out his hand for the glass.

“Certainly.” He handed over the lens, and while the London investigator knelt to look at the stain, Lord Darcy said to Master Sean: “I would be much obliged, my dear Sean, if you would make a similarity test on that stain. I should like to know if it is blood, and, if so, whether it is Sir James’ blood.” He narrowed his eyes thoughtfully. “And while you’re at it, do a thorough check of the bloodstain around the body. I should like to be certain that all of the blood is actually Sir James Zwinge’s.”