the host (reluctant, unresisting) still?

In accordance with the law of the conservation of energy.

Why was the host (secret infidel) silent?

He weighed the possible evidences for and against ritual murder: the
incitations of the hierarchy, the superstition of the populace, the
propagation of rumour in continued fraction of veridicity, the envy of
opulence, the influence of retaliation, the sporadic reappearance of
atavistic delinquency, the mitigating circumstances of fanaticism,
hypnotic suggestion and somnambulism.

From which (if any) of these mental or physical disorders was he not
totally immune?

From hypnotic suggestion: once, waking, he had not recognised his
sleeping apartment: more than once, waking, he had been for an
indefinite time incapable of moving or uttering sounds. From
somnambulism: once, sleeping, his body had risen, crouched and
crawled in the direction of a heatless fire and, having attained
its destination, there, curled, unheated, in night attire had lain,
sleeping.

Had this latter or any cognate phenomenon declared itself in any member
of his family?

Twice, in Holles street and in Ontario terrace, his daughter Millicent
(Milly) at the ages of 6 and 8 years had uttered in sleep an exclamation
of terror and had replied to the interrogations of two figures in night
attire with a vacant mute expression.

What other infantile memories had he of her?

15 June 1889. A querulous newborn female infant crying to cause and
lessen congestion. A child renamed Padney Socks she shook with shocks
her moneybox: counted his three free moneypenny buttons, one, tloo,
tlee: a doll, a boy, a sailor she cast away: blond, born of two dark,
she had blond ancestry, remote, a violation, Herr Hauptmann Hainau,
Austrian army, proximate, a hallucination, lieutenant Mulvey, British
navy.

What endemic characteristics were present?

Conversely the nasal and frontal formation was derived in a direct
line of lineage which, though interrupted, would continue at distant
intervals to more distant intervals to its most distant intervals.

What memories had he of her adolescence?

She relegated her hoop and skippingrope to a recess. On the duke's lawn,
entreated by an English visitor, she declined to permit him to make and
take away her photographic image (objection not stated). On the South
Circular road in the company of Elsa Potter, followed by an individual
of sinister aspect, she went half way