a similarity between our sample and his, we identified it as a mushroom known as the Devil's Throne. The fungus is dried, minced, and steeped in brandy or other spirit. The liquid is then decanted off and the minced bits are thrown away—or, sometimes, steeped a second time. In large doses, the drugged spirit results in insanity, convulsions, and rapid death. In small doses, the preliminary stages are simply mild euphoria and light intoxication. But if taken regularly, the effect is cumulative—first, a manic, hallucinatory state, then delusions of persecution and violence."
Lord Darcy's eyes narrowed. "That fits. Thank you. Now there is one more problem. I want positive identification of that corpse. My Lord Bishop is not certain that it is his brother; that may just be wishful thinking. My Lady Marquise refuses to view the body, saying that it could not possibly be her husband—and that is definitely wishful thinking. But I must know for certain. Can you make a test?"
"I can take blood from the heart of the dead man and compare it with blood from My Lord Bishop's veins, my lord."
"Ah, yes. The Jacoby transfer method," said Lord Darcy.
"Not quite, my lord. The Jacoby transfer requires at least two hearts. It is dangerous to take blood from a living heart. But the test I have in mind is equally as valid."
"I thought blood tests were unreliable between siblings."
"Well, now, as to that, my lord," Master Sean said, "in theory there is a certain very low probability that brother and sister, children of the same parents, would show completely negative results. In other words, they would have zero similarity in that test.
"Blood similarity runs in a series of steps from zero to forty-six. In a parent-child relationship, the similarity is always exactly twenty-three—in other words, the child is always related half to one parent and half to the other.
"With siblings, though, we find variations. Identical twins, for instance, register a full forty-six-point similarity. Most siblings run much less, averaging twenty-three. There is a possibility of two brothers or two sisters having only one-point similarity, and, as I said, my lord, of a brother and sister having zero similarity. But the odds are on the order of one point seven nine million million to one against it. Considering the facial similarity of My Lord Bishop and My Lord Marquis, I would be willing to stake my reputation that the similarity would be substantially greater than zero—perhaps greater than twenty-three."
"Very well, Master Sean. You have not failed me yet; I do not anticipate that you ever will. Get me that data."
"Yes, my lord. I shall endeavor to give satisfaction." Master Sean left suffused with a glow of mixed determination and pride.
Lord Darcy finished his pipe and headed for the offices of Captain Sir Androu Duglasse.
The captain looked faintly indignant at Lord Darcy's question. "I searched the castle quite thoroughly, y' lordship. We looked everywhere that M' Lord Marquis could possibly have gone."
"Come, Captain," Lord Darcy said mildly, "I don't mean to impugn your ability, but I dare say there are places you didn't search simply because there was no reason to think my lord of Cherbourg would have gone there."
Captain Sir Androu frowned. "Such as, my lord?"
"Such as the secret tunnel."
The captain looked suddenly blank. "Oh," he said after a moment. Then his expression changed. "But surely, y' lordship, you don't think . . ."
"I don't know, that's the point. My lord did have keys to every lock in the castle, didn't he?"
"All except to the monastery, yes. My Lord Abbot has those."
"Naturally. I think we can dismiss the monastery. Where else did you not look?"
"Well . . ." The captain hesitated thoughtfully. "I didn't bother with the strongroom, the wine cellar, or the icehouse. I don't have the keys. Sir Gwiliam would have told me if anything was amiss."
"Sir Gwiliam has the keys, you say? Then we must find Sir Gwiliam."
Sir Gwiliam, as it turned out, was in the wine cellar. Lord Seiger informed them that, at Lady Elaine's request, he had sent the seneschal down for another bottle of brandy. Lord Darcy followed Captain Sir Androu down the winding stone steps to the cellars.
"Most of this is used as storage space," the captain said, waving a hand to indicate the vast, dim rooms around them. "All searched very carefully. The wine cellar's this way, y' lordship."
The wine-cellar door, of heavy, reinforced oak, stood slightly ajar. Sir Gwiliam, who had evidently heard their footsteps, opened it a little more