WARNING: The following contains spoilers for Shadow's House, Episode 3, "The Soot Sickness," now streaming on Funimation.
Episode 3 of Shadow's House opens with Emilico meeting up with her cleaning squad for her second lesson: how to find her way around the house, from the hall where the Living Dolls keep their protective costumes and tools to the upper floors where the adult dolls live. As Rosemary and Mia share their knowledge with Emilico and Lou, the alarm bells go off. A phantom is launching an attack, and all the Living Dolls must coordinate to destroy it.
A phantom is a malevolent entity that forms when smaller soot scorches coalesce into a single blob. While individual scorches are closer to angry mice than terrifying eldritch horrors, a phantom is a different matter. They can shapeshift from a hydra beast to an arachnid, with basic but effective intelligence that drives them to hide before striking.
Emilico's squad follows what they think is a single scorch to a gallery room, where the soot creature has hidden behind a large painting. As they're about to hit it with the mop, the real phantom lurches toward them, getting hold of Rosemary's head and quickly covering her entire face with soot. Then it grows legs -- think of Stranger Things' Mind Flayers -- using its strength to lift Rosemary off the floor and try to hang her from the ceiling. Mia quickly maneuvers herself under Rosemary's feet to keep her from dying, but the soot phantom has enough control over her to try and kick Mia in the face -- and without a perfect face to emote her Shadow Mistress' emotions, Mia could be "discarded."
However, water makes phantoms brittle, so Lou uses her cleaning flask to spray some droplets on it. It works, but she doesn't have enough to affect most of the creature's body. Emilico and Lou quickly fear they'll have to pick which life they save: Mia's or Rosemary's. But with quick thinking, Emilico jumps and grabs an elevated flower base, throwing the water at the phantom and dissolving it into wet soot, freeing Rosemary.
Lou is relieved, congratulating Emilico on her ability to think outside the box. After all, the Dolls are conditioned to clean, so spilling a whole vase of water and making a mess to save their mentor seemed impossible to Lou. However, the nightmare isn't over. Rosemary survived, but her eyes are pitch black, her skin pale, her expression unresponsive and her body keeps throwing itself against a wall and falling on the floor. These are the symptoms of soot sickness -- which only the Healing Squad can treat.
The next day, all the Living Dolls are scheduled to take a long bath to fully clean the soot off, and Rosemary comes back from her shower right as rain. She explains to Emilico that soot sickness is relatively easy to treat. The Doll's system can be flushed by drinking lots of water, but it must be done quickly or it could end in death or worse.
However, the real plot twist of Episode 3 is that Kate was as surprised to learn about the Phantoms as Emilico. Nothing in her supposedly comprehensive Shadow studies mentioned them -- and they should, because Phantoms are made of soot that manifests whenever the Shadows are experiencing negative feelings. It has Kate wondering what other secrets are being kept from her.
Shadow's House, based on the manga by Somato, is created by CloverWorks, directed by Kazuki Ōhashi, and written by Toshiya Ōno, with character design by Chizuku Kusakabe and music by Kenichiro Suehiro. It is currently streaming on Funimation.