‘It’s even better from the roof.’ Ace crossed to a door in the far wall and unlocked it, handing the bottle and the tracker to Yaz. ‘Don’t open the bottle in the apartment. I’ll be up in a minute.’

Yaz hesitated for a moment then nodded and made her way up the narrow stairs.

Ace watched her go, then stepped back into the apartment, picked up the holdall and made her way up to her bedroom.

Dumping the holdall on the bed, she stared at her reflection in the mirror. God, she looked tired. She had forgotten what life with the Doctor was like. No wonder her travelling companions were getting younger – they had to be, just to keep up with her. She figured that Graham had to be permanently knackered. The thought of him made her smile.

She picked up a small, spherical pendant on a chain from the bedside table, removed one of the marbles from her holdall, snapped open the pendant and slipped the Nitro ball inside. Then she closed the pendant up again and hung it around her neck.

As she crossed to the door, a dark shape in the corner of the room caught her eye. Her old jacket. For all her complaints, being around the Doctor made you feel … young again.

On impulse she lifted the jacket from its hook and slipped it on. It had been 30 years since she had last worn it and it felt like yesterday. She was suddenly aware that putting it on meant something.

It was time to put old demons to bed.

Graham stood in the monitor room of the alien transit station, tapping his toe against a gristly fold in the floor. It made a quiet, obscene squelching noise that was horrible but somehow compulsive.

The place was a pit, and he hated it. Alien ships that were plastic and metal could be cold and creepy but at least Graham understood something of what held them together. They were just your space equivalent of buses, only with star bells and warp whistles and galactic go-faster stripes. Even the TARDIS, for all its glowing crystal immensity, was packed with tech. The station, though, felt all wrong. Standing there, Graham felt like a bug in the middle of a burnt-black steak that had been chewed up and spat out, and you didn’t know when sharp teeth might bite down again.

He looked at the blue block of the TARDIS, savoured its paintwork, windows and solid straight lines, a sane refuge in this damp cavern of a craft. Wires and cables snaked out of the open doors to a console on a stand, the size and shape of a portable barbecue. The Doctor stood hunched over it; the Squidget was perched on top of a clunky old computer monitor, its thin tentacles connecting it to the weirdly rippling walls of the spacecraft.

‘How’s it going now, Doc?’ Graham asked.