Jarn and Mari moved OK, but Kapur blundered blindly, and Tsedi and Kueht seemed unaccustomed to the lack of gravity. The siblings stayed as close to each other as they could get in the confined space, touching and twittering like birds. Mari growled to herself, imagining what the master-at-arms would have said about that.

They couldn’t have gone more than a few hundred metres before Mace’s cloak turned blue. But Kapur, bathed in a cerulean glow he couldn’t see, refused to leave Mace behind. He toiled doggedly on, his inert burden on his back.

Jarn snapped, ‘I don’t have time for this. Gunner, sort it out.’

‘Sir. How?’

‘With the tact and sensitivity you starbreaker grunts are famous for. Just do it. You two, move on.’ She took the lead again, hustling Tsedi and Kueht behind her.

Mari took her place behind Kapur, at a loss. ‘. . . I guess you knew each other a long time, sir.’

Kapur turned. ‘Mace and I? How old are you, gunner?’

‘Eighteen standard, sir.’

‘Eighteen.’ He shook his head. ‘I first met Mace before you were born, then. I was seconded here by the Commission, on the failed first contact with the Snowflake.’

‘Seconded?’

‘I was a Guardian, a policeman. As the Expansion grows, the rate of Assimilation itself accelerates, and specialists are rare . . . My own brand of forensic intelligence proved adequate for the role. My job was to understand the Snowflake. Mace’s was to destroy it.’

Mari understood the tension. Resources were always short. The Assimilation, the processing of newly contacted alien species on an industrial scale, followed an accelerating Expansion that now spanned a quarter of the Galaxy’s disc and had reached the great globular clusters beyond.

And, in one of those clusters, they had found the Snowflake. It surrounded a dwarf star, a tetrahedron fourteen million kilometres on a side: a stupendous artefact, a vast setting for an ancient, faded jewel of a star.

So far as anybody knew, the Snowflake had been constructed to observe: simply that, to gather data, as the universe slowly cooled. Since the building of the Snowflake, thirteen billion years had shivered across the swirling face of the Galaxy.

Assimilation was a matter of processing: contact, conquest, absorption - and, if necessary, destruction. If Kapur had been able to determine the goals of the Snowflake and its builders, then perhaps those objectives could be subverted to serve human purposes. If not, then the Snowflake had no value.

Mari guessed, ‘Lieutenant Mace gave you a hard time.’

Kapur shook his head. ‘Mace was a good officer. Hard, intelligent, ambitious, brutal. He knew his job and he carried it out as best he could. I was in his way; that was uncomfortable for me. But I always admired him for what he was. In the end the Snowflake resisted Mace’s crude assaults.’

‘How?’

‘We were - brushed aside.’