Skidding to a halt, she jabbed her blackened car aerial into the sticky substance of the wall beside her. Then she pressed the sonic against it and buzzed hard.

The wall shuddered and groaned as a gristly creeper – a power cable – was drawn out through the thick morass. With no cutting tools, the Doctor bit into the creeper and pulled on it hard. Thick amber oil spurted out from the creeper at high pressure, throwing the Doctor back, spluttering, as the two horse-creatures rounded the corner.

‘Centaurions, stop!’ she yelled.

Ignoring her, the Astingir kept coming but as they splashed into the tide of slick oil their hooves slid from under them. One fell, dropping its spear as it landed hard. The other centaurion stumbled over the hindquarters of its fellow and smashed its head against the wall with a roar.

The Doctor turned and ran on.

‘Graham!’

‘Doctor?’ Graham heard her shouts echo down the dark access corridor and her footfalls as she approached.

‘I felt the ship power up. Who was it, Ryan or Yaz? Did you mark the trail, did you—?’

‘It was Ace! They took Ace!’ Graham yelled back. ‘Get in here!’

‘Ace?’ Wide-eyed, clothes stained with stinking brown goo, the Doctor skidded back inside. ‘They can’t have taken her! She—’

‘Doesn’t have a tag, yeah, so she didn’t show on this thing, did she?’ He kicked the console. ‘Yaz told me, she said they were attacked by those rat-things.’

‘She’s safe?’

‘I think so—’

‘Was she wearing the pheromone slime?’

Graham nodded. ‘Said it made no difference!’

‘I don’t understand.’ The Doctor suddenly tensed, looked behind her. ‘But! First things first. We’re about to be charged by a pair of very angry – and now quite slippery – centaur warriors.’

‘Of course we are!’ Graham groaned.

‘We need to hold them off long enough to trail Ryan when he gets taken.’ She concentrated hard. ‘But how?’

‘What about the TARDIS force field?’ Graham said. ‘If you could sort of project it out here …?’

‘Yes! Extrude the force field. Brilliant.’ Abruptly she dashed off into the TARDIS. ‘Keep watching the console!’

‘What if they don’t take Ryan?’ Graham called after her. ‘Didn’t work with Yaz, did it? Maybe that gunky stuff’s not even important …?’

But even as he spoke, he felt the same tension coiling through the floor beneath him, a waft of that same vile smell. Graham felt his heart pound to a halt as the red light snapped on. He reached for the lever, slammed it home.

The walls exploded around him as a gigantic tremor tore through the station, flinging Graham to the ground in a shower of filth and ichor. Squidget convulsed, its tentacles writhing. The lights dipped and the floor lurched beneath him. The howling alarm started up again, a shriek of pain.

Pain and, this time, despair.

CHAPTER SEVENTEEN

‘Doc?’ Graham shouted. ‘What the hell was that?’