“The ceylon orchid is very responsive to changes in humidity,” says Syracuse, indicating a ragged little purple thing, “and the pendula there will indicate if the temperature goes above sixty-eight degrees. Stelitzia for raised voices, amaryllis for electromagnetic fields, and this little Ecuadorian will know if any of the other flowers move more than an inch from their relative positions.”

“This is so much trouble,” says Naff. “I could get you a digital security system for—”

“The digital can be hacked. Subverted. Disabled. Trust the analog.”

“How do they tell you when things change, anyway?”

She studies him. “They die.”