Isaac is Joshua's little brother.  He also was Sandeman's favourite and he told Joshua to protect him.  Unlike Joshua, he has a barcode. He was kind and caring. When "Father" left, he became sad and kept howling and crying.  The Manticore guards beat him until they cut out his tongue. This made Isaac angry.

   When he escaped, he came to Seattle. The sector police reminded him of the Manticore guards and he would attack them and rip out their tongues as a trophy.  Joshua tried to stop him and protect stop ended up captured himself.

   Isaac attacked Max and Joshua and tried to stop him but ended up killing him.