On board the "Centauri", the defect which caused Kryten to blow up his head is fixed. There Kryten meets another mechanoid named Able who is a servant to the Simulant and who, it turns out, is from the same batch as Kryten (a 4000 series) and carries the same serial number. This means that Kryten and Able are, in effect, brothers. However, Able is a "zoney"—he is addicted to a narcotic known as "otrazone" that is specially designed for mechanoids. Abuse of this has corrupted Able's circuit boards. Thanks to Kochanski's navigating skills, the crew soon end up in a standoff with the Simulant who, to prove he means business, gives Kryten the password to a secure file in his CPU that he's never been able to access. Lister is able to knock out the Simulant and "Starbug" flees with the rescued mechanoid brothers.