The Sontaran Stratagem

Martha Jones is back in her new job as medical officer for UNIT, a worldwide army dedicated to fighting alien menaces. But the menace is bigger than ever as the threat of ATMOS spreads across the world. Donna discovers that even her own family is not safe from the alien threat – but is it too late to save them?

Martha summons the Doctor back to modern-day Earth, but an old enemy lies in wait – the Sontarans. Having covertly established a base at the mysterious ATMOS Factory aided by the Rattigan Academy, the Sontarans soon unleash a potent terror which brings the world to its knees…