Mrs. Tantrumi was the (supposedly) sweet old lady who had the light orb that was given to Dr. Burrows. Evidently, she loves cats as she three of them who follow her around the house. She turned out to be a fraud when it was discovered that she was a Styx agent.
When Dr. Burrows was chasing the man-in-a-hat, he came upon Mrs. Tantrumi's house. She owned the house where the luminescent orb was first found. She invites him inside for tea, and the doc agreed. She lets him look around her basement, where the orb was found and when he discovers the strange articles of clothing, Mrs. Tantrumi claims to know nothing.
When Dr. Burrows and Will are in Highfield, they come upon Mrs. Tantrumi's house. Dr. Burrows decides to talk to her, to find out if Oscar Embers really was a Styx agent. She again invites them in for tea and biscuits, and chats with Dr. Burrows about the light orb. She tells him to check in the basement. While he goes down, she attacks him with a knife, but is hit on the head with a biscuit tin by Will. After Will holds the ludicrous lady back, he and Dr. Burrows escape outside, where Drake is waiting. Will informs Drake, who goes downstairs to kill her. However, she is gone by the time Drake gets down.
- "Orlando! Mind your manners, you naughty boy! I'm so sorry, Dr. Burrows. He's not used to strangers. I hope he didn't scratch you."
- "Your time is coming! Nobody escapes the Colony!"
- "DEAD! YOU ARE BOTH DEAD! [...] THERE ARE TOO MANY OF US!"
- One of the cats that always follows her around (depicted as terribly thin and ginger) is called Orlando.