There is a prison from which it is said that no one attempts to escape. The reason is that the prison is guarded by the fearsome Iron Lizards: self-propelled bombs that are able to locate and destroy a person, due to their DNA being inputted in a miniature computer inside the lizard. Lupin and company learn that Fujiko is being held captive by the warden, who wants to have sex with her. In order to save her, Lupin, Jigen and Goemon get inside the prison, but end up captured by the warden who enters their genetic data into the Iron Lizards.
In the English dub, the episode was renamed Lair of the Land-Shark due to the Iron Lizards resembling a shark more-so than a lizard.