The dig proceeds with the Doctor and the other slaves making progress, but when Toba abandons his watch post Jamie and Cully disable another Quark and free their friends. The Doctor has worked out the Dominator scheme: a nuclear fission seed will be dropped down the borehole, converting the entire planet into a radioactive mass to power the Dominator fleet. They begin digging a tunnel to the central borehole to steal the deadly device before it can detonate. Jamie and Cully help by destroying Quarks with homemade bombs.