'My view' the Doctor said 'is that you can run - in fact it's often by far the best option - but you can't hide.  I'll see myself out.'

Nyssa felt a pang of disappointment.  He had gone.  She would probably never see him again.

The town of Oxford in AD 1278 seems a haven of tranquility.  Under the summer sun, merchants, students and clerics go about their daily, unhurried tasks.  Alfric, the proctor of the Franciscan friary, has only two minor problems: one of the friars has gone missing, and there's a travelling showman, calling himself the Doctor, with a pretty young noblewoman by his side, attracting crowds in the narrow streets.

When the missing friar is found dead, the Doctor is convinced he has been murdered.  There is a ruthless killer at large, and Alfric reluctantly teams up with the Doctor to track him down.

Their investigation leads towards the most celebrated of the Franciscan brotherhood: Roger Bacon, famed throughout Christendom as a scholar - and, in the far future, the subject of a revolutionary thesis by technographer Nyssa of Traken.

'Take Arcadia apart if you have to.'

The middle of the twenty-fifth century. The Dalek war is drawing to an untidy close. Earth's Office of External Operation is trying to extend its influence over the corporations that have controlled human-occupied space since man first ventured to the stars.

Agent Isabelle Defries is leading one expedition. Among her barely-controllable squad is an explosives expert who calls herself Ace. Their destination: Arcadia.

A non-technological paradise? A living laboratory for a centuries-long experiment? Fuel for a super-being? Even when Ace and Benny discover the truth, the Doctor refuses to listen to them.

Nothing is what it seems to be.

'Danger is my middle name,' Ace said, 'or it would be if I had more than one.  I can look after myself these days, you know.'

Freedom.  LIberty.  Free will.  Independence.  Choice.  Everyone wants to be free.  But at what point does freedom become irresponsibility?  What happens when one person's choice causes another's oppression?

The Doctor's on a simple mission to return a communications device he borrowed years previously.  Being a Time Lord, he can return it before anyone misses it.

But events in the Mendeb system have moved more quickly than the Doctor estimated, and he lands in the ruins of a civilisation devestated by mysterious invaders.