“Now let us see. We think these triangles, which wander aimlessly all about the castle, represent Pellenore. Does that assumption make sense to both of you?”

Brit and Nimue nodded.

“Good. Then there are these stars, which also drift around but only on one side of the Great Hall. I surmise those stand for Mordred, right?”

Again, they indicated their agreement.

“And there are the crosses. If we were to connect them in a continuous line, we’d find them heading in a somewhat roundabout way for the refectory. Those may very well be Lancelot. That leaves our Mr. X. The Xs go in a more or less direct way toward Arthur’s tower, where the killing took place. And our most probable guess for his identity is Mark of Cornwall.”

“But Merlin,” Nimue said, “the key word in what you said is guess. Arthur wants proof. He’ll never agree to convict anyone based on guesswork with nothing concrete to back it up. Suppose the crosses are Mordred and the stars Lancelot? How can we prove it one way or the other?”

“We have statements from the suspects themselves. And we have what the servants saw, or in Gretchen’s case, more than simply saw.”

Nimue smiled at this.

“But there must be more of them. Ganelin would not have marked this chart without some basis. There must be more servants we have not identified yet who saw one or more of our suspects that night. I intend to find those servants. Ganelin found them; I will, too.”

“But-” Something was bothering Brit and it showed. “We are still simply assuming Mark is the fourth suspect. We don’t know. No one saw him, that we know of. Suppose it’s someone else? Or suppose that trail of Xs goes somewhere other than to Arthur’s tower? The chart doesn’t extend that far. And suppose Mark really is Mr. X as you call him. Just because a servant saw him in the corridor is hardly proof he committed murder.”

“Well, someone saw him-or rather someone saw some-one-because the chart is marked. Whether it was Mark… well, that seems likely to me. But that is what I want the two of you to discover.” He sat back in his chair. Nimue had never seen him quite so stern; it was clear his wounded leg and hand were causing him pain. “In Cornwall.”

Brit registered alarm. “You want us to go to Mark’s territory? After the attack we suffered?”

“Arthur is sending official word to Mark that you will be visiting him, to discuss some military maneuvers for next spring. And you will have a larger escort than the one we had. He won’t dare harm you.”

“If he is the villain.” Brit said this emphatically.

“He is.”

“How can you sound so confident?”

“Because, Brit, of the attack on you, or on Petronus, at the garrison in Corfe. The guards were killed. They would never have let Lancelot get that close to them. Or anyone else, for that matter. Except Mark. They would have recognized him as the commander of the army, and they would have let him approach, never expecting him to strike them.”

“Good point.”

Nimue studied the chart, looking doubtful. “But still, we’ll be terribly vulnerable.”

“You have the advantage of knowledge. Mark doesn’t know that we know.”

“He must suspect, at least, or why follow and attack us?”

“He knows we know he’s up to something. He can’t possibly know we think he is the murderer. And as I’ve said before, the very fact that the man we suspect is also the head of the king’s armed forces makes for a very delicate situation. How can we know what kind of loyalty he has among the other commanders, and among the troops? I can’t tell you how deeply I hope I’m wrong about this. But everything I know suggests Mark is the one.”

“I can find out about the other commanders.” Brit was looking increasingly unhappy. “I can make some discreet inquiries, among knights I know I can trust.”

“When you get back from Cornwall. And remember, you mustn’t do anything to force Mark’s hand. Be subtle, be indirect and pick up whatever you can learn. Use all the guile you have.”

“Guile isn’t much good against armed swordsmen, Merlin. ”

“No, but it is priceless against blunt stupidity.”

“Why do I not find that comforting?”

“Arthur will provide a large enough escort to keep you safe. Discover what you can.”

Looking unhappy, or at least severely dubious, Nimue and Brit rose to go. Just as they were leaving, Merlin said, “And Colin? Use all the guile you have.”

“Uh… yes, Merlin.”

Nimue followed Brit down the stairs, past the spot where she’d found Ganelin. Suddenly Brit turned on her. “What did he mean by that?”

“I-I don’t know.”

“Who are you? Where did you come from?”

“I don’t know what you mean. My name is Colin. You know that.”

“There has been talk about a young woman who fled from Morgan’s court. Mordred’s betrothed. She disappeared about the time you came here.”

“N-no.”

Merlin appeared at the top of the staircase. “Come back here, both of you.”

Slowly, sullenly, they climbed back to his study.

He closed the door behind them and leaned against it, wincing from the pain in his leg. “Now, Brit, what exactly are you suggesting?”

“Someone from Morgan’s court may be here in Camelot. And there have been murders. Can you not guess what I’m thinking?”

“Colin was with me in the Great Hall when Borolet was killed.”

“Are you certain? You yourself just said that he’s full of guile.”

He sighed sadly and looked at Nimue. “Tell her.”

“But I-”

“Tell her!”

And so Nimue confessed to Brit that she was not really Colin, not really a boy at all.

“So you see, Brit,” Merlin added when she was done, “I’ve known all along. I’ve encouraged Nimue to carry on this masquerade.”

Brit looked doubtful. “What have you known? How can you know what loyalty she feels to Morgan le Fay?”

“There is no doubt in my mind. Colin-Nimue is loyal to Arthur and Camelot and everything it represents. I’ve heard her complain about Morgan’s superstitious nonsense often enough. And no one sane could want to marry a horror like Mordred.”

Brit was unconvinced but kept quiet.

“We can’t start fighting among ourselves, Brit. We have to trust each other. This kind of squabbling is the worst thing we can do.”

“I suppose you’re right.”

“I am and you know it. Time is short. Midwinter is approaching fast, and it is more important than ever. It may be the last chance we have to lure Mark here unsuspecting.”

“But without proof-”

“I can provide proof. I’ve commented recently about using people’s superstitions against them. And Mark is as gullible as anyone. That will be his undoing. But we need him to come here, unsuspecting and without his guard up. Ensuring that will be your job. When you get to Cornwall, comfort him, flatter him, make him believe his position is secure.”

“Merlin, I want to know what you’re up to. What are you planning?”

“In time, Brit. Go to Cornwall. Everything depends on the two of you getting Mark to lower his guard.” Softly, he added, “Please. We are too far into this investigation to let it come apart now.”

And so the next morning Merlin saw Brit and Nimue off to Cornwall. Their carriage was larger and heavier-and better protected-than the one they’d used on their visit to Morgan, and a detachment of sixteen armed soldiers escorted them.

Just before they left, Nimue took Merlin aside. “I’m afraid, Merlin. She doesn’t trust me. And how sure are you that she isn’t loyal to Mark?”

“Brit is one of my oldest, closest friends here. I’m as sure of her as I can be of anyone.”

“Mark is one of Arthur’s oldest friends, remember? And Britomart thinks I’m working for Morgan.”

“I’ve noticed the tension between the two of you before. I was never certain what caused it. But it will pass. Get to know her. You’ll like her and she’ll like you.”