Visiting the planet Penadron, the Fourth Doctor is about to visit the Senate, but a coded message from an anonymous source allows him to realise in time that the Senate are actually malevolent, intending to kill him to extract all his knowledge from his brain.
- The message is written in code.
- The illustration depicts a robot-like being, similar to the K1 robot from Robot. It is not clear to which element of the narrative it corresponds; it is possible that it is intended to depict a member of the Penadronian species, which is not physically described in the narrative.
- The coded message was actually written in code and left for readers to decipher themselves, allowing the story to double as a game.