“Kaygi Haza was like many gentrymen in this fashion. He had a small circle 
of officers he met with, encouraged, and occasionally gave gifts to---and 
Jolgalgan was also one such officer. For how else could she have known of 
his bath? How else could she have so easily navigated the servants’ passageways, 
and known which door to use? The answer is, Kaygi Haza had brought her there before 
himself, likely many times—as a friend.” A languid wave of her hand, acknowledging her
point. “Now that Jolgalgan was in the estate, she then used her knowledge
and her altered vision to navigate the dark passageways without a light,
ascending to the roof. And there, she delivered the killing blow, dropping
the dappleglass into the boiler above the steam room. At that point, her goal
here was accomplished. Jolgalgan rejoined the party and left with the
throng. Kaygi Haza took his steams after the party—and then, sadly, he was
to perish before the morning.

[...]

“That is a fascinating tale,” Fayazi said finally. “But you have not
mentioned anything untoward or dangerous. You have given no indication,
for example, of how the ten Engineers were also poisoned, if they were
even at my house---nor how any of this might threaten me.”

“I am glad you asked,” said Ana, grinning. “For that question
confounded me for a goodish bit. Yet then I realized…We already knew that
the poisoning of the Engineers was different from the deaths of both Kaygi
Haza and Commander Blas. They died much later, at irregular times, and
their blooms issued from different parts of their bodies. This suggests they
were poisoned differently, too.” She turned her blindfolded face to me. “Din
saw the answer, of course. He just didn’t know.”

Everyone looked at me. I simply frowned, for I had no idea at all what
she meant.

“Madam Haza,” said Ana. “Am I correct in recalling that your father
had a bejeweled ewer from which he enjoyed drinking wine?”

Fayazi reluctantly said, “He did. He had several, in fact.”

“I see. And did he often enjoy drinking wine,” asked Ana softly, “while
he took his bath?”

Lightning danced up my bones then, and the memory surfaced in my
mind: there, in the old man’s bath, a stone ledge; and all along it, many
faded red rings from many past wine cups.

“He… he did…” said Fayazi

“Then it’s as I thought,” said Ana. “On that very night, in his bath,
Kaygi Haza enjoyed a cup of wine from his favorite ewer, right as the air
was full of steam—and dappleglass spores. The ewer he drank from sat
open to the air and was now tainted. And that same ewer was then used later
at this secret meeting of Kaygi Haza’s favored Engineers, to pour the wine
for all those young people who had come to indulge themselves. And then
they drank. They drank, unaware that whatever poured forth from such a
vessel now carried death itself—inevitable, painful, and awful.”

A HORRIFIED SILENCE hung over the courtroom.

“Truly?” asked Vashta, aghast. “Do you truly think this is how such a
tragedy began?”

“I am almost completely certain,” said Ana. “That would explain why it
took so much longer for the infections to—what is the word—to bloom. For
the Engineers had likely consumed fewer spores than Kaygi Haza himself,
and those who drank more wine died fastest. But none had sat and soaked in
the spores and breathed them in, like the elder Haza did. I also suspect the
spores succeed more in the lungs than the stomach. But still they succeeded,
eventually. And all ten perished.”

- The Tainted Cup, Chapter 37 pgs. 330-332