 The SID uses a new type of metal detector in its pursuit of the castaways. The detector is programmed to key in on an alloy that is only found on Earth. They hide any and all objects made of the alloy except for one. Unfortunately, the one object they can t hide is a surgical pin in Dan s leg, which was used to fix a broken leg he suffered while competing in the Olympics. They then decide to try to contact their old friend Dr. Brule, who is now in prison after he was caught helping them when Barry needed an operation to remove his appendix. However, Brule and his nurse are being forced by Kobick and the warden at the prison to go ahead with the operation as a way to capture Dan and the others.