Top-secret Station 7 is where the Earth Forces send all the equipment captured in their unceasing war against the Daleks. It's where Dalek technology is analysed and examined. It's where the Doctor and Amy have just arrived. But somehow the Daleks have found out about Station 7 - and there's something there that they want back. With the Doctor increasingly worried about the direction the Station's research is taking, the commander of Station 7 knows he has only one possible, desperate, defence. Because the last terrible secret of Station 7 is that they don't only store captured Dalek technology. It's also a prison. And the only thing that might stop a Dalek is another Dalek.