“I remember.  She gave evidence at the inquest.”

“Precisely.  Well, she brought me some plans belonging to her father which she found.  He was engaged in a quiet job hereabouts five years ago, and died when it was finished.  He was poisoned with arsenic.”

“What! like that man Tyke?”

“Yes.  The person who runs this show—­Maraquito, I think—­ evidently has a partiality for that extremely painful poison.  Well, this workman having constructed the secret entrance, was got out of the way by death, so that the secret might be preserved.  And I guess Miss Loach was settled also in case she might give the alarm.”

“But if the secret entrance is in the cottage,” said Twining, “this old woman may have been aware of its existence.”

“Certainly, and was about to split when she was killed.  At least, that is my theory.”

“She must have been in with the gang.”

“I have never been able to fix that,” said Jennings thoughtfully.  “I know she was a lady and of good birth.  Also she had money, although she condemned herself to this existence as a hermit.  Why she should let Maraquito and her lot construct a secret entrance I can’t understand.  However, we’ll know the truth to-night.  But you can now guess, Twining, how the bell came to be sounded.”

“No, I can’t,” said the inspector, promptly.

“I forgot.  You don’t know that the secret entrance is in the room where Miss Loach was murdered.  Well, one of the gang, after the death, sounded the bell to call attention to the corpse, and then slipped away before Susan Grant could get to the room.”

“But why should this person have sounded the bell?”

“That is what I have to find out.  There’s a lot to learn here.”

“Have you any idea who killed Miss Loach?”

“Maraquito, under the disguise of Mrs. Herne.”

“Was she Mrs. Herne?”

“Yes.  She masqueraded as an invalid who could not leave her couch, but I managed to get at the truth to-night.”

“But from the evidence at the inquest, Mrs. Herne was out of the house when the blow was struck.”

“Quite so:  But we did not know of this secret entrance then.  I fancy she came back—­”

“But how can you—­”

“There’s no more time to talk,” interrupted Jennings.  “We must get to work as soon as possible.  Order your men to surround the house.”

“And the park also?”

“We have not enough men for that.  And I don’t think there’s any other exit from the factory save that through Rose Cottage.  If there was, Maraquito and her two friends would not have played whist so persistently with Miss Loach every night.”

“It was three times a week, I think.”

“Well, it doesn’t matter.  Here we are.”  Jennings opened the garden gate and walked boldly up the path towards the silent house.  The men, under the low-spoken directions of Twining, spread themselves round the house so as to arrest any coiner who might attempt escape.  Then the detective rang the bell.  There was no answer for a few minutes.  He rang again.