On her day off, Catherine has to come to the office to meet with Max, with her granddaughter Hannah in tow. Max has brought Catherine in for a cold case, in which Sasha Khan was supposedly killed by noxious fumes. Mimi Khan, her sister, woke up from a four-year coma and says Sasha's death wasn't an accident. Sasha's body is being exhumed. Catherine leaves Hannah with Folsom and Allie while she and Serena go to interview Mimi, who is accompanied by her friend Heather. Sasha says Sasha's husband Ken broke into the salon that night. Hannah ends up going to the well-preserved crime scene with the team. Folsom's analysis proves that someone had tampered with the bottles in the salon. The team interviews Ken, Sasha's son William, and all the former employees, to examine any drama at the salon. The ventilation system had been sabotaged. Allie finds a hair, likely from the killer, left in a fungus growing in the ventilation system. The killer was using a hair-loss drug, as Ken did. Mimi recalled a gray-faced monster with a snout. Catherine didn't tell Lindsay that she took Hannah to a crime scene. Catherine finds out an old cord in Max's stash that allows Chris to get into Sasha's phone. A selfie includes a shadow that could be a monster. Catherine receives an unhappy text from Lindsay. Ken is allergic to the hair-care drug the killer used. Folsom determines that the salon was selling knockoff products. Catherine figures out that the killer was wearing a gas mask, which would have looked like a snout. The killer tripped and smashed the mask's filter, leaving charcoal and plastic debris. Mint residue Beau finds points to Heather, Mimi's mint-loving friend. Heather also used the same hair-loss drug. Sasha had caught Heather substituting the knockoffs.