62
Saxitoxin, which has the chemical formula C10H17N7O4 and is named after the clam Saxidomus giganteus in which it was first discovered, is a neurotoxin or nerve poison produced by a small number of species of dinoflagellate phyto-plankton. These microscopic life-forms are ingested by other, bigger species such as shellfish and puffer fish, most commonly when the waters which the fish inhabit are affected by ‘algal bloom’. This occurs when the population of algae, including the types of plankton that contain saxitoxin, multiplies rapidly, covering the water with a thick layer of red or brown scum. The fish eat the plankton, humans eat the fish, and then the humans are struck down by a condition known as paralytic shellfish poisoning, or PSP.
Saxitoxin is heat resistant, so cooking cannot nullify its effect. Once it has been consumed, symptoms appear within minutes and include any or all of the following: a feeling of nausea, followed by diarrhoea and/or vomiting and/or abdominal pain; tingling and/or burning sensations in limbs and extremities, including hands, feet, lips, gums and even the tongue; shortness of breath and choking; confused and/or slurred speech; and loss of limb coordination. Someone who has saxitoxin poisoning could easily be mistaken for a drunk. The crucial difference is that a hard night’s boozing will only give you a hangover. PSP, however, can very easily be fatal. In fact, saxitoxin is so dangerous that a single dose of 0.2 milligrams is enough to kill an average human. That makes it approximately a thousand times more toxic than sarin nerve-gas.
Naturally, the CIA became very, very interested in saxitoxin. Back in the fifties, its undercover operatives were supposedly given suicide capsules containing it, but in 1970 the agency was ordered to destroy its entire stock by, ironically enough, that most toxic of all presidents, Richard Milhous Nixon.
Saxitoxin, however, did not go away. Nature kept on producing it, and precisely because of its effects on the nervous system medical researchers discovered it could be an extremely effective laboratory tool. In time, scientists discovered how to synthesize it, using the methods described by Carver to Klerk. It had proved relatively simple for Klerk’s people to replicate the process so painstakingly mapped out in the Journal of the American Chemical Society and then mix extremely high doses of saxitoxin, many times greater than that needed to kill, into the flour and water used to make communion wafers. The baking process did nothing to make the wafers any less poisonous. The intensity of the poison, however, ensured that its effects would be felt far more quickly than those of a naturally inflicted dose of PSP.
The timing was a delicate issue, though. It was absolutely vital that Carver reach the end of the line of communicants, dosing them all, before anyone realized that anything had happened. Ideally, he wanted a few extra seconds in which to attack Mabeki before he too was alerted. Finally, it was essential to coordinate the timing of everything he did downstairs with that of Zalika’s theft of the diamonds upstairs.
Zalika was in the master bedroom. She had located the safe, hidden behind another portrait of the Gushungos. Now she was reaching into her canvas shoulder-bag and retrieving the envelope Tina Wong had given her. She opened it and pulled out a clear, sealable plastic sandwich-bag. Inside the bag was a thin latex glove, of the kind worn by surgeons. Zalika removed it and placed it on her right hand. Then she turned back to the safe.
Faith Gushungo accepted her wafer with uncharacteristic meekness. Then Carver moved on to the bodyguards kneeling on the floor behind. From the corner of his eye, he saw Moses Mabeki slip from the room. He thought he heard Mabeki’s footsteps first in the hallway and then slipping up the stairs.
Zalika was up there, unarmed and unaware that she was in danger of detection.
But there was no way Carver could warn her that Mabeki was loose inside the house without blowing his own cover.
And if that were not enough, he had a more immediate problem to consider, the one that had struck him just before the service. And with every step he took, it was getting closer.