In the Stonekeeper, Theodore was first seen when he appeared out of a small door when Silas Charnon died. Miskit had told Theodore to place Silas in a sleeping chamber and prepare Silas for transport to Kanalis. Theodore is also seen at the very end where he and Ruby have to secure all loose items and furniture and also not forget any passengers.
Theodore is seen at the beginning when he is carrying plates to Miskit in the kitchen. His plates suddenly all topple off as Navin Hayes tries to control the Charnon House. Miskit makes Sausage, Toast, Bacon and Scrambled Eggs that Theodore has to take to Emily. He also tells her that they would be arriving in Kanalis soon.
When they arrive in Kanalis, Theodore, Cogsley, Ruby and some other robots have to stay in to look after the Charnon House. After elves attack the hospital in Kanalis for Emily, they are also going to storm the Charnon House. Cogsley then does a complete shutdown in result that all the robots still in the Charnon House are turned off so the elves cannot get any information. During the shutdown, Navin then eventually comes to turn them back on. He says to Theodore, "I'll get you out of here, Theodore." After Navin plugs the memory stick, Theodore and all the other robots come alive.
After the Charnon House catches Emily and Leon Redbeard, Morrie and Theodore rush outside to take Leon and Emily inside. When Luger throws a fit at the Charnon House, the roof cracks where Morrie and Theodore are standing. Emily soon fixes it.
Theodore is seemed to have a quiet personality as he hardly talks. He does all his orders as told and correctly. Thus making him reliable and responsible.
"I'll get you out of here, Theodore." - Navin to Theodore
"!" - When the Charnon House trembled
"Yes sir." - To Miskit after receiving an order
"We will be arriving in Kanalis soon." - To Emily about arriving
"Thank you Theodore." - Emily to Theodore