Voriet cleared his throat and activated his data-slate.

‘Draven Sark,’ he said reluctantly. ‘The local annals have no listings for anyone of that name, so it appears that Draven Sark was never a resident of, or visitor to, Gershom. However, he is in the Subsector Census. Current age two hundred and fifty-one standard, whereabouts unknown. A very high-ranking and respected magos medicae in his day. His grandfather is an interesting figure, a senior recollector in the Administratum. His name was Lemual Sark, and he secured his footnote in history four centuries ago through his research on Symbol Iota, which led to a breakthrough in the battle against a virulent pestilence known as Uhlren’s Pox.’

‘Also known as blood-froth, or the Torment,’ said Jaff. ‘It was a pandemic. Sark’s work was crucial in containing–’

‘I am familiar with the case,’ said Eisenhorn. ‘Sark was able to confirm that Uhlren’s Pox was not a natural contagion or a xenos plague, but in fact a weapon deliberately bio-engineered by a servant of the Archenemy.’

‘Really?’ asked Macks.

Eisenhorn looked at her. ‘That detail has been classified and withheld from the general population, marshal. I have just un-classified it. So Draven Sark is a descendant?’

‘That’s the case, sir,’ said Voriet. ‘The whole Sark family line has been engaged with Materia Medica for many generations, either as medicae experts or medicae specialists serving the Administratum. In Draven Sark’s case, the former. He retired decades ago.’

‘Whereabouts unknown?’ asked Eisenhorn.

‘Yes,’ said Voriet. ‘But it appears he continued to practise on a private basis. In retirement, he assumed several identities. Sadrane Carnac, Philipo Bosk, Emment Pelet…’

‘Why does a respected medicae take on assumed names?’ asked Macks.

Voriet smiled.

‘The circumstances of his retirement are sealed,’ he said. ‘One may presume malpractice, and a quiet effort to avoid scandal. Draven Sark and his various alter egos have been persons of interest to both the Arbites and the ordos at different times over the last century. He has a history of unfortunate associations. Nothing that could lead to prosecutions, but enough to convince me he walks in the shadows of lawlessness.’

Voriet scrolled through his slate.

‘Some seventy years ago,’ he said, ‘Philipo Bosk was listed as a resident of Gershom, specifically of Unkara Province. He owned property here, paid his tithes, was listed as “retired”.’

‘Where were his properties?’ asked Eisenhorn.

‘Unknown,’ said Voriet. ‘A great number of municipal records were lost during the civil war. All trace of Philipo Bosk vanishes about twenty years ago. But we have picts of him, and comparative recognition cogitation confirms within an error margin of decimal zero-zero-two per cent that Bosk and Sark are the same man.’

‘So, he disguises his identity, but not well,’ said Betancore. ‘A simple verification reveals the truth. That seems clumsy.’