This is the 1st novel published by the BBC to feature the 8th Doctor.  His companion is Samantha "Sam" Jones.

The Doctor, while checking on the Eye of Harmony, is ensnared in a trap set by the Master.  He forgets who he is but trusts the TARDIS.  It takes him on a journey through time to correct problems that had arose with his other selves.  As he meets each of his past selves more of his memory is restored.

In the end, the Doctor materializes in Totters Lane to rescue Sam from Baz Bailey and they both take off in the TARDIS.

The TARDIS materialised.

The door opened and the Doctor stepped outside.  He stood for a moment, surveying the scene before him.

He was at the top of a steep hill.  Below him lay a long wide valley, through which meandered a broad, winding river.

At his back, and on either side were rolling, heather-covered hills, stretching away to distant mountains.  Here and there, banks of mist clung to the hill tops.

The Doctor considered what to do.  The TARDIS had brought him here, just as it had taken him to the junkyard and the jungle.  Presumably his other self, his next regeneration was somewhere near. The logical thing was to go and look for him.

And there, at his feet was a moorland path, leading towards a narrow valley between two low hills.

As he strode briskly along, the Doctor reflected that retracing his own steps through time might prove rather a dangerous business.  Clouded though most of his his [sic] memories still were, something told him that he had lived extremely eventful lives.

What had the angry old man in the jungle said?  Seven regenerations - six other selves still to be met!  So many lives, so many adventures, so many friends - and enemies - all forgotten, all lost to him.

Still, he knew who and what he was now.

A Time Lord of Gallifrey.

A fugitive Time Lord, perhaps?  Certainly that was how the First Doctor had thought of himself.

The Doctor shook his head as if trying to rattle his memories into life.  What attitude had his people taken to his defection?  Had they simply ignored it?  Or were they angrily hunting him down?  He didn't feel like a fugitive.

Perhaps there had been some kind of reconciliation?  A lot could happen in half a dozen lifetimes.

Drawing in deep breaths of the crisp, clean air, the Doctor told himself that for once his quest had taken him somewhere peaceful and pleasant.  There was a fresh, unspoiled quality to this open, rolling landscape - an unpolluted, pre-industrial, dawn-of-time sort of feeling.

Then he heard the sound of horses' hooves and the tramp of marching feet.  A troop of soldiers appeared in the valley before him.  Ahead came a standard-bearer, carrying a long pole which bore the image of a fierce golden eagle.  Below the eagle were the initials SPQR.

Behind the standard-bearer was a chariot, drawn by two tired horses.  An officer marched beside the chariot, and behind him marched weary ranks of armoured men.  They wore breastplates and helmets with horse-hair crests.  They carried square shields, javelins and short swords.

Romans, thought the Doctor, and immediately wondered how he knew.  He stepped forwards, raising his hand in salute.  'Hail!'

Astonished, the officer raised his hand.  'Halt!'

The charioteer reined in his horses, and the ranks of marching soldiers came to a halt.  Tired as they were, they made no attempt to break ranks.  They stood alert, grasping their swords and spears, awaiting orders.