'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.