Immediately a waiting double posse of determined-looking men advanced from the station across two intervening tracks, one lot sprouting press cameras, the other notebooks. George stepped down from the train to meet the notebook people, and the others fanned out and began clicking. One of the notebook crowd climbed aboard and came into the dining car, inviting anyone who had seen anyone or anything suspicious the previous evening to please unbutton, but of course no one had, or no one was saying, because otherwise the whole train would have known about it by now.

The investigator said he would try his luck with the scenery-watchers in the dome-car, with apparently the same result, and from there he presumably went in to see the Lorrimores, who apart from Xanthe were still in seclusion. He then reappeared in the dining car with an interested crowd of people following him and asked to speak to Xanthe, who up until then had kept palely quiet.

He identified her easily because everyone looked her way. Filmer was still beside her: the passengers tended all the time to linger at the tables, talking, after the meals had been cleared, rather than return to the solitude of their bedrooms. Nearly everyone, I would have guessed, had been either in the dining room or the dome car all morning.

Mrs Young squeezed Xanthe's hand encouragingly from across the table while the half-child half-young-woman shivered her way through the dangerous memory.

'No,' she said, with everyone quiet and attentively listening, 'no one suggested I went to our car… I just wanted to go to the bathroom. And I could… I… could have been killed.'

'Yes… 'The investigator, middle-aged and sharp-eyed, was sympathetic but calming, speaking in a distinct voice that carried easily through the dining car, now that we weren't moving. 'Was there anyone in the dome car lounge when you went through?'

'Lots of people.' Xanthe's voice was much quieter than his.

'Did you know them?'

'No. I mean, they were on this trip. Everyone there was.' She was beginning to speak more loudly, so that all could hear.

A few heads nodded.

'No one you now know was a stranger?'

'No.'

Mrs Young, intelligent besides comforting, asked, 'Do you mean it's possible to uncouple a car while you're actually on the train? You don't have to be on the ground to do it?'

The investigator gave her his attention and everyone leaned forward slightly to hear the answer.

'It's possible. It can be done also while the train is moving, which is why we want to know if there was anyone in the dome car who was unknown to you all. Unknown to any of you, I should say.'

There was a long, respectful, understanding silence.

Nell said, 'I suppose I know most of our passengers by sight by now. I identified them all at Toronto station when I was allocating their sleeping quarters. I didn't see anyone yesterday evening who puzzled me.'

'You don't think,' Mrs Young said, putting her finger unerringly on the implication, 'that the car was unhitched by someone in our party'?'

'We're investigating all possibilities,' the investigator said without pompousness. He looked around at the ranks of worried faces and his slightly severe expression softened. 'The private car was deliberately uncoupled,' he said, 'but we're of the preliminary opinion that it was an act of mischief committed by someone in Carder, the last place you stopped before Miss Lorrimore found the car was missing. But we do have to ask if the saboteur could have been on the train, just in case any of you noticed anything wrong.'

A man at the back of the crowd said, 'I was sitting in the dome car lounge when Xanthe came through, and I can tell you that no one had come the other way. I mean, we all knew that only the Lorrimores' car was behind the dome car. If anyone except the Lorrimores had gone that way and come back again… well… we would have noticed.'

Another nodding of heads. People noticed everything to do with the Lorrimores.

I was watching the scene from the kitchen end of the dining car, standing just behind Emil, Cathy and Oliver. I could see Xanthe's troubled face clearly, and also Filmer's beside her. He seemed to me to be showing diminishing interest in the enquiry, turning his tidily brushed head away to look out of the window instead. There was no tension in him: when he was tense there was a rigidity in his neck muscles, a rigidity I'd watched from the depths of the crowd during the brief day of his trial and seen a few times since, as at Nottingham. When Filmer felt tense, it showed.

Even as I watched him, his neck went rigid.

I looked out of a window to see what he was looking at, but there seemed to be nothing of great note, only the racegoing passengers streaming off their forward carriages en route to write postcards home from the station.

Filmer looked back towards Xanthe and the investigator and made a small gesture of impatience, and it seemed to trigger a response from the investigator because he said that if anyone remembered any helpful detail, however small, would they please tell him or one of his colleagues, but meanwhile everyone was free to go.

There was a communal sigh as the real-life investigation broke up. Zak, I thought, would be finding the competition too stiff, the fiction an anti-climax after the fact. He hadn't appeared for this scene: none of the actors had.

Most of the passengers went off to don coats against what appeared to be a cold wind outside, but Filmer climbed down from the door of the dome-car end of the dining car without more protection than his carefully casual shirt and aristocratic tweed jacket. He paused irresolutely, not scrunching, as the others were beginning to, across the two sets of rails between our train and the station but meandering at an angle forwards in the direction of the engine.

Inside, I followed him, easily keeping pace with his slow step. I thought at first that he was merely taking an open-air path to his own bedroom, but he went straight past the open door at the end of his sleeping car, and straight on past the next car also. Going to see his horse, no doubt. I went on following: it had become a habit.

At the end of the third car, just past George Burley's office, he stopped, because someone was coming out from the station to meet him: a gaunt man in a padded short coat with a fur collar, with grey hair blowing in disarray in the wind.

They met between George's window and the open door at the end of the car and although at first they looked moderately at peace with each other, the encounter deteriorated rapidly.

I risked them seeing me so as to try to hear, but in fact by the time I could hear them they were shouting, which meant I could listen through the doorway without seeing them or being seen.

Filmer was yelling furiously, 'I said before Vancouver.'

The gaunt man with a snarl in his Canadian voice said, 'You said before Winnipeg, and I've done it and I want my money.'

'Cooee' trilled Daffodil, teetering towards them in chinchillas and high-heeled boots. 'Are we going to see Laurentide Ice?'