He departed, and within thirty-six hours the house and office of Cowperwood, the house of Butler, the office of Harper Steger, Cowperwood’s lawyer, and Cowperwood and Aileen separately and personally were under complete surveillance.  It took six men to do it at first, and eventually a seventh, when the second meeting-place, which was located in South Sixth Street, was discovered.  All the detectives were from New York.  In a week all was known to Alderson.  It bad been agreed between him and Butler that if Aileen and Cowperwood were discovered to have any particular rendezvous Butler was to be notified some time when she was there, so that he might go immediately and confront her in person, if he wished.  He did not intend to kill Cowperwood—­and Alderson would have seen to it that he did not in his presence at least, but he would give him a good tongue-lashing, fell him to the floor, in all likelihood, and march Aileen away.  There would be no more lying on her part as to whether she was or was not going with Cowperwood.  She would not be able to say after that what she would or would not do.  Butler would lay down the law to her.  She would reform, or he would send her to a reformatory.  Think of her influence on her sister, or on any good girl—­knowing what she knew, or doing what she was doing!  She would go to Europe after this, or any place he chose to send her.

In working out his plan of action it was necessary for Butler to take Alderson into his confidence and the detective made plain his determination to safeguard Cowperwood’s person.

“We couldn’t allow you to strike any blows or do any violence,” Alderson told Butler, when they first talked about it.  “It’s against the rules.  You can go in there on a search-warrant, if we have to have one.  I can get that for you without anybody’s knowing anything about your connection with the case.  We can say it’s for a girl from New York.  But you’ll have to go in in the presence of my men.  They won’t permit any trouble.  You can get your daughter all right—­we’ll bring her away, and him, too, if you say so; but you’ll have to make some charge against him, if we do.  Then there’s the danger of the neighbors seeing.  You can’t always guarantee you won’t collect a crowd that way.”  Butler had many misgivings about the matter.  It was fraught with great danger of publicity.  Still he wanted to know.  He wanted to terrify Aileen if he could—­to reform her drastically.

Within a week Alderson learned that Aileen and Cowperwood were visiting an apparently private residence, which was anything but that.  The house on South Sixth Street was one of assignation purely; but in its way it was superior to the average establishment of its kind—­of red brick, white-stone trimmings, four stories high, and all the rooms, some eighteen in number, furnished in a showy but cleanly way.  It’s patronage was highly exclusive, only those being admitted who were known to the mistress, having