With a snort of anger, the Astingir slammed her hand against the control and the door began to slide open.

Graham turned and ran for his life.

The pounding of hooves echoed around the dark, gristly corridors. Graham felt the blood pulse in his temples as he ran, each gasp for breath like a hook in his throat. He turned right through an open doorway into a corridor where the floor was smothered with vine-like cables, and began running like he’d done as a kid through the tyres in the school obstacle race, knees high, trying not to trip. Would it slow down the centaurs? He prayed it would.

There was a shaft leading off to his left and he threw himself into it. Perhaps they wouldn’t realise he’d ducked off the main corridor and keep racing on. That was possible, wasn’t it? Wasn’t it?

The sound of hooves was coming closer. They were still after him. Could horses hunt? These weren’t horses. They were aliens, and angry as hell.

Graham glanced back and saw a glint of golden armour. A laser bolt flashed past and blackened the wall beside him. Chest tight, legs beginning to cramp, he tried to go faster. There was a door to his right and he dodged through it. It gave onto some sort of wide-open space with six steaming, scaly cylinders – cooling towers, perhaps – rising up from the floor. A hiding place! Perhaps he could get inside one of them and …

The Astingir’s energy blast hit the floor so close behind him it threw him onto his face. For a few seconds he was stunned, dizzy. He rolled onto his back and saw Legate Aquillon canter slowly into the chamber, Masst and another centaurion at her side.

‘My enemy’s friend is my enemy,’ said Aquillon. ‘For your many crimes, I condemn you to die.’

She raised her crossbow, the laser bolt beginning to form.

Graham closed his eyes, as they filled with tears, for Ryan, for Yaz, for the Doctor.

See you soon, Grace, love, he thought, as he heard the spit and sizzle as the bolt fired.

But it never hit him. Graham opened his eyes, in time to witness a second bolt bounce away as if deflected by the air itself.

‘That idea you had, Graham,’ came a familiar voice behind him. ‘The one about extruding the TARDIS force field to protect us? That was proper genius, that was!’

Graham looked round and saw the Doctor beaming and Yaz rushing forward to help him up. He grabbed her in a happy embrace, squeezing her tight.

‘Oh, you two!’ he cried, clutching hold of the Doctor too.

‘Where’s Ryan?’ Yaz asked, anxious.

‘He vanished, just now. This stupid place boosted him on to wherever those Ratts wanted to take him.’ Graham held the Doctor’s eyes. ‘Doc, I was so scared, I thought they’d killed you.’