The Night Beyond the Tricornered Window - Season 1 Episode 3 Malediction

Mikado and Hiyakawa go to investigate a pond at a house. Their client, the woman who owns the house, has the same dream every night of a corpse floating in the pond. Mikado dives down into the pond to have a look, and there at the bottom, in the murk, he sees its core. On their way home that day, Mikado and Hiyakawa stop to eat and Hiura Erika appears before them. Erika reveals to the two of them that she is a curse peddler and a necromancer.