"yes the TARDIS will keep us safe and don't worry Caitlyn, He will be fine he cant die after all," The DOctor said "Not that the illness is one that would kill." he knew his friend just needed rest and medicine "He'll still feel awful."
he knew that while he was weak was an easy moment for the Master to kidnap and torture Jack. He was glad they were safe for now in the TARDIS, He didn't want the Master harming JAck when he couldn't defend himself.