held in a vacuum chamber and the ‘viewing’ is carried out on a closed-circuit television screen positioned beside the apparatus itself.
Typically, the SEM offers a range of magnifications from about fifteen up to around two hundred thousand, allowing progressively finer and finer details of the object to be observed. The sample needs to be very carefully prepared to withstand the vacuum inside the chamber, and also has to be modified to conduct electricity because the sample is scanned with a stream of electrons, not light waves. This process is usually done by coating it with a very thin layer of gold.
Once made ready, the specimen is placed carefully on a small tray attached to the inside of the door of the vacuum chamber, the door itself is then closed and sealed and the air pumped out. Once a vacuum has been created, a gun at the top of the microscope fires a beam of electrons downwards through a series of magnetic lenses, which focus the beam on a very tiny area.
That spot of energy is then moved backwards and forwards across the surface of the sample by a series of coils: this is the ‘scanning’ part of the SEM. As the beam hits the specimen, secondary electrons are dislodged from its surface. These are counted by a detector, which sends the information to an amplifier, and the final image that appears on the screen is created by counting the electrons emitted by the sample.
‘I don’t know,’ the technician replied. ‘It looks like some kind of a spore, but not one I’ve ever seen before.’
‘Where did it originate?’
‘I found it in the scrapings from the dining table in the house belonging to this man Spiros Aristides – the index case.’
The black-and-white image of a handful of spherical objects appeared on the screen – because the SEM uses electrons the image will never appear in colour, although printed images often have false colour added. The detail generated by the equipment was remarkable, but even with a magnification of one hundred and fifty thousand there was, frankly, little to see: just a collection of tiny spore-like items.
‘Actually,’ the technician said, swiftly readying the electron microscope to receive the second specimen, ‘that wasn’t what I wanted you to see.’ As soon as the vacuum had been dispelled she unlocked and pulled open the airtight door, then removed the first specimen and replaced it with the second one. ‘When I saw those things, I wondered if they were lying dormant. So I added a small amount of water to a second sample, prepared that for the SEM and then examined it too. This,’ she finished, as the screen came to life, ‘is what I wanted you to look at.’
The supervisor leaned closer, his mouth dropping open in astonishment. The microscopic spherical objects were still there, but all, without exception, had burst open and the sample was now a mass of what looked like virus particles, but not, the supervisor noted immediately, with the characteristic thread-like shape of a filovirus.
‘Well, the good news is it’s definitely not Ebola or Marburg,’ he said. ‘The bad news is that I don’t know what it is. If I had to guess, I’d say it was some kind of bovine virus. The only thing I’ve seen that looks anything like it is BLV – Bovine Lymphotrophic or Leukaemia Virus – but that makes no sense at all. That virus only infects cattle and it’s very slow-acting: it attacks the lymph glands and can eventually cause cancer. There’s no way that it can kill a healthy human being in less than twenty-four hours.’
For Richter, time seemed to have stopped. He hung motionless in the water, figuring the angles. He could see the two demolition charges under the seat in front of him and he knew perfectly well that if either or both of them exploded the biggest remnant of his body anybody might subsequently find would be a tooth.
Naturally, that worried him. What also worried him was the fact that the charges he could see appeared to have been tossed into the cabin at random: for a proper demolition job they should have been placed in strategic locations to ensure the total destruction of the aircraft. The casual manner in which they had been dumped suggested that possibly there were others scattered under the seats, in the piles of debris, or even outside the fuselage.
They now had, he realized, exactly two choices: they could quickly search the cabin and try to locate and defuse all the charges before they went off or they could get the hell out of there. It wasn’t a difficult decision for him.
Richter whirled round and gestured upwards with his thumb. Crane nodded and the two men immediately swam out of the gaping hole in the front of the cabin and headed back along the thin cord Crane had paid out towards the detached wing. With imminent death lurking in the dark waters behind them, they moved as quickly as they could.
They passed the Learjet’s wing, and began to swim even faster, following the cord towards the lead anchor and the rope that led to the buoy up on the surface. Crane spotted it first, braked abruptly and began swimming upwards, his left hand grabbing and then encircling the rope. Richter was right behind him all the way.
In the wreckage of the Learjet, the four pencil detonators had been active for a little over two hours and forty minutes, so the remaining thickness of membrane separating the switches and batteries from the sea water could now be measured only in microns. Making chemical-activated detonators has never been an exact science, because there are so many different circumstances that cannot be factored in. The water depth and hence the pressure, the water temperature, and even the force used to snap the end of the pencil and initially arm the detonator: all could affect the time elapsing before the device would explode. The fuses Stein had collected from Souda Bay were of good quality, pretty much state of the art, but still they were going to blow some minutes before the full three hours were up.
Richter and Crane deliberately slowed their pace as they ascended – going up to the surface too fast kills more divers than almost anything else because it doesn’t allow the absorbed nitrogen in the blood to come out of solution gradually. Crane had arranged aqualung sets at twenty and then at ten feet below the surface, and Richter slowed himself even further as they approached the lower of the two sets. But Crane waved him on, and they stopped together just ten feet below the surface, seizing hold of the buoy cable.
Crane started his stopwatch, then checked his dive watch. He then consulted a dive table printed on a plastic board attached to his weight belt and made some swift calculations, working out how long they’d been submerged and at what depths. These two factors would determine the length of time they had to spend decompressing before they could surface safely. Once he’d arrived at an answer, he did the whole check over again.
At this point Crane wrote ‘WHAT THAT?’ on the waterproof board and passed it across to Richter, who had just opened the air valve on one of the two aqualung sets attached to the buoy cable and swapped mouthpieces.
Richter took the pencil and scribbled ‘BOMB’ in reply, then added ‘WHEN SURFACE?’ below it. Crane checked his stopwatch and wrote ‘6 MIN’. Richter wrote: ‘TOO LONG – GO UP IN 4’. The diving officer at first shook his head, but both he and Richter ascended as soon as four minutes had elapsed, clambered into the life raft and tore off their masks.
‘You shouldn’t fuck around with decompression tables,’ Crane warned, adding ‘sir’ as a grudging afterthought. ‘It’s too dangerous.’
‘Not half as dangerous as getting your head blown off by fifty pounds of plastic,’ Richter retorted.
‘We were down at about one hundred feet for over thirty minutes,’ Crane said. ‘We should have decompressed for nine minutes at ten feet. I cut two minutes off that time, which is dangerous enough, and you lopped another two minutes off that, meaning we surfaced four minutes too early.’
Richter grinned at him across the life raft. ‘
‘Not fucking likely,’ Crane replied. ‘What were those packages?’
‘They were modified demolition charges. Normally they’re made up of four half-pound sheets of C4 plastic explosive, so each one contains just under one kilo, but the ones down there looked a lot bigger, maybe a couple of kilos or more. C4 is very efficient and you really don’t want to be around when it goes off.’
‘Are we safe here?’ Crane asked.
‘No idea,’ Richter replied. ‘It depends how much explosive’s actually been placed in that wreck. I spotted just two charges, but there could easily be others scattered in the debris or under the fuselage. Where’s that fucking chopper?’
