"Look here," cried the young woman, "if you don't let me pass to
untie him I'll run outside and scream for the police."

"I should not advise you, Miss MacNab," said Dr Hood gravely,
"to be in any hurry to fetch the police. Father Brown,
I seriously ask you to compose your flock, for their sakes, not for mine.
Well, we have seen something of the figure and quality of Mr Glass;
what are the chief facts known of Mr Todhunter? They are substantially three:
that he is economical, that he is more or less wealthy, and that
he has a secret. Now, surely it is obvious that there are
the three chief marks of the kind of man who is blackmailed.
And surely it is equally obvious that the faded finery,
the profligate habits, and the shrill irritation of Mr Glass
are the unmistakable marks of the kind of man who blackmails him.
We have the two typical figures of a tragedy of hush money:
on the one hand, the respectable man with a mystery; on the other,
the West-end vulture with a scent for a mystery. These two men
have met here today and have quarrelled, using blows and a bare weapon."

"Are you going to take those ropes off?" asked the girl stubbornly.

Dr Hood replaced the silk hat carefully on the side table,
and went across to the captive. He studied him intently,
even moving him a little and half-turning him round by the shoulders,
but he only answered:

"No; I think these ropes will do very well till your friends
the police bring the handcuffs."

Father Brown, who had been looking dully at the carpet,