The police think they know better.

They do know this much, that it could not have been a case of suicide, that if the man who undoubtedly travelled with Mrs.Hazeldene on that fatal afternoon had no crime upon his conscience he would long ago have come forward and thrown what light he could upon the mystery.
"As to who that man was, the police in their blindness have not the faintest doubt.

Under the unshakable belief that Errington is guilty they have spent the last few months in unceasing labour to try and find further and stronger proofs of his guilt.

But they won't find them, because there are none.

There are no positive proofs against the actual murderer, for he was one of those clever blackguards who think of everything, foresee every eventuality, who know human nature well, and can foretell exactly what evidence will be brought against them, and act accordingly.
"This blackguard from the first kept the figure, the personality, of Frank Errington before his mind.