The Saint encounters a monster mystery in Scotland - none other than the baffling Loch Ness Monster. Is it responsible for macabre killings, or is a human hand behind it all?
The Second Doctor and Jamie visit space station Camera to speak to the scientist Dastari, but the station has a saboteur aboard, as Chessene is working with the Sontarans.
The Doctor and Peri meet Jamie and learn the Second Doctor is with the Sontarans in Spain. At a hacienda, Chessene and the Sontarans set up base.
Chessene and Shockeye succumb to their baser instincts and revert to their Androgum ways, while the Sontarans prepare the Second Doctor to trigger their Kartz-Reimer capsule.
A French fencing match provides the telling clue in a murder and Inspector Goron travels to London to assist March.