Terror Keep

Terror Keep is one of the Mr J G Reeder books by Edgar Wallace. RIGHTLY speaking, it is improper, not to say illegal, for those sadly
privileged few who go in and out of Broadmoor Criminal Asylum, to have
pointed out to them any particular character, however notorious he may
have been or to what heights of public interest his infamy had carried
him, before the testifying doctors and a merciful jury consigned him to
this place without hope. But often had John Flack been pointed out as he
shuffled about the grounds, his hands behind him, his chin on his breast,
a tall, lean old man in an ill-fitting suit of drab clothing, who spoke
to nobody and was spoken to by few.

"That is Flack--the Flack; the cleverest crook in the world...Crazy John
Flack...nine murders..."

This is the third story in the J G Reeder series. Old John Flack has escaped from prison and revenge against Reeder is on his mind.