Victor rubbed his hands together happily.

‘Sounds like a faked death. How do we go about hunting down a dead man?’

Jeff held up a fax.

‘I’ve had to use up a lot of favours at the English Medical Council; they don’t like giving out personal files whether the subject is alive or dead, but here it is.’

Victor took the fax and read out the pertinent points.

‘Theodore Mьller. Majored in physics before pursuing a career in medicine. Struck off in ‘74 for gross professional misconduct. He was a fine tenor, a good Hamlet at Cambridge, Brother of the Most Worshipful Order of the Wombat, keen train-spotter and a founder member of the Earthcrossers.’

‘Hmm,’ I murmured. ‘It’s a good bet that he might continue to indulge himself in old hobbies even if he was living under an assumed name.’

‘What do you suggest?’ asked Victor. ‘Wait until the next steam train extravaganza? I understand the Mallard is defending her speed record next month.’

‘Not soon enough.’

‘The Wombats never disclose membership,’ observed Bowden.

Victor nodded. ‘Well, that’s that, then.’

‘Not exactly,’ I said slowly.

‘Go on.’

‘I was thinking more about someone infiltrating the next Earthcrossers meeting.’

‘Earthcrossers?’ said Victor with more than his fair share of incredulity. ‘You’ve got no chance, Thursday. Weird lunatics doing strange things privately on deserted hillsides? Do you know what you have to go through to be admitted to their exclusive club?’

I smiled.

‘It’s mostly distinguished and respected professional people of mature years.’

Victor looked at Bowden and myself in turn.

‘I don’t like that look you’re giving me.’

Bowden quickly scoured a copy of the current Astronomer’s Almanac.

‘Bingo. It says here that they meet on Liddington Hill at two p.m. the day after tomorrow. That gives us fifty-five hours to prepare.’

‘No way,’ said Victor indignantly. ‘There is no way, I repeat, no way on God’s own earth that you are going to get me to pose as an Earthcrosser.’

Liddington Hill overlooks the RAF and later Luftwaffe airfield of Wroughton. The low hill is also home to an Iron Age fort, one of several that ring the Marlborough and Lambourn downs. The antiquity of the site, however, was not what attracted the Earthcrossers. They had gathered in almost every country of the globe, following the peculiar predictions of their calling in an apparently random fashion. They always observed the same routine: name the site, do a very good deal with the owners for exclusivity, then move in the month before using either local security or more junior members of the group to ensure that no infiltrators find their way in. It was perhaps due to this extreme secrecy that the militant astronomical group managed to keep what they did absolutely quiet. It seemed an almost perfect hiding place for Dr Mьller, who co-devised the society in the early fifties with Samuel Orbiter, a notable television astronomer of the time. Victor parked his car and walked nonchalantly up to two huge gorilla-sized men who were standing next to a Land Rover. Victor looked to the left and right. Every three hundred yards was a group of armed security men with walkie-talkies and dogs, keeping an eye out for trespassers. There was no way on earth that anyone could slip by unseen. The best means of entering anywhere you aren’t allowed to go is to walk in the front door as though you own the place.

‘Afternoon,’ said Victor, attempting to walk past. One of the gorillas stepped into his way and put a huge hand on his shoulder.

‘Good afternoon, sir. Fine day. May I see your pass?’

‘Of course,’ said Victor, fumbling in his pocket. He produced the pass inserted behind the worn plastic window of his wallet. If the gorillas took it out and saw that it was a photocopy, then all would be lost.

‘I haven’t seen you around before, sir,’ said one of the men suspiciously.

‘No,’ replied Victor evenly, ‘you’ll see from my card that I belong to the Berwick-upon-Tweed spiral arm.’

The first man passed the wallet to his comrade.

‘We’ve been having problems with infiltrators, isn’t that so, Mr Europa?’

The second man grunted and passed the wallet back to Victor.

‘Name?’ asked the first, holding up a clipboard.

‘I probably won’t be on the list,’ said Victor slowly. ‘I’m a latecomer. I called Dr Mьller last night.’

‘I don’t know of any Dr Mьller,’ said the first, sucking in air through his teeth as he looked at Victor with narrowed eyes, ‘but if you are an Earthcrosser you will have no problem telling me which of the planets has the highest density.’

Victor looked from one to the other and laughed. They laughed with him.

‘Of course not.’

He took a step forward but the smile on the men’s faces dropped. One of them put out another massive hand to stop him.

‘Well?’

‘This is preposterous,’ said Victor indignantly. ‘I’ve been an Earthcrosser for thirty years and I’ve never had this sort of treatment before.’

‘We don’t like infiltrators,’ said the first man again. ‘They try to give us a bad name. Do you want to know what we do to bogus members? Now. Again. Which of the planets has the highest density?’

Victor looked at the two men, who looked back at him menacingly.

‘It’s Earth. The lowest is Pluto, okay?’

The two security men were not yet convinced.

‘Kindergarten stuff, mister. How long is a weekend on Saturn?’

Two miles away in Bowden’s car, Bowden and I were frantically calculating the answer and transmitting it down the line to the earpiece that Victor was wearing. The car was stuffed with all sorts of reference books on astronomy; all that we could hope was that none of the questions would be too obscure.

‘Twenty hours,’ said Bowden down the line to Victor.

‘About twenty hours,’ said Victor to the two men.

‘Orbital velocity of Mercury?’

‘Would that be aphelion or perihelion?’

‘Don’t get smart, pal. Average will do.’

‘Let me see now. Add the two together and—Ah, good Lord, is that a ringed chaffinch?’

The two men didn’t turn to look.

‘Well?’

‘It’s, um, 106,000 miles per hour.’

‘Uranus’s moons?’

‘Uranus?’ replied Victor, stalling for time. ‘Don’t you think it’s amusing that they changed the pronunciation?’

‘The moons, sir.’

‘Of course. Oberon, Titania, Umb—‘

‘Hold it! A real Earthcrosser would have logged the closest first!’

Victor sighed as Bowden reversed the order over the airwaves.

‘Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck, Miranda, Ariel, Umbriel, Titania and Oberon.’

The two men looked at Victor, nodded and then stepped back to let him pass, their manner changed abruptly to acute politeness.

‘Thank you, sir. Sorry about that but, as I’m sure you realise, there are very many people who would like to see us stopped. I’m sure you understand.’

‘Of course, and may I congratulate you on your thoroughness, gentlemen. Good-day.’

As Victor walked by they stopped him again.