Suppose with me a moment, that Agatha, Milverton's housemaid had a father in London, an honest laborer, let us call him Mr. Pitman, who was pleased and proud that his only daughter had caught the eye of a rising young tradesman, the enterprising plumber Escott. And that he knew that his darling daughter was not going to grow old as a spinster in domestic service, and that, having opened her heart to another, for the first time, her love was returned, and that she planned to marry. Could any father have been other than happy in Victorian London? But then, horror of horrors, his dearest daughter is abandoned, left alone, jilted, her hopes and dreams dashed. For what reason? None stated. The cad just walked out on his fiancee. Well, if that father had any gumption he would have had something to say about it -- a few days work would surely reveal the true identity of the plumber (OK, you may disagree, but bear with me, this is my fantasy) who at the very minimum was guilty of breach of promise, an action which was taken far more seriously then than now. So Agatha's father, in high dugeon, takes his pickax, and mounts the stairs to 221B, but does not tell Holmes he is Agatha's father. The dialog might have included something such as the following --

"Mr. Holmes," said Pitman after describing the situation, "would you undertake to find the cad who deserted my daughter after promising marriage?"

"I am afraid, sir", said Holmes, a trifle nervously, "that my schedule is too busy to accept cases that do not present unique or abstruse features, and yours seems to be devoid of such qualities. Furthermore, the difficulties in finding a man given as few clues as you have given me seem almost insurmountable. While I sympathize with your distress, I regret that I must tell you that I think you will never discover Mr. Escott."

"On the contrary," said Pitman quietly; "I have every reason to believe that I will succeed in discovering Mr. Escott."

Holmes gave a violent start and dropped his pipe. "I am delighted to hear it," he said.

"Delighted that your cruel abuse is discovered Mr. Holmes?"

Holmes sprang out of his chair and picked up his pipe. "I cannot waste time over this sort of fantastic talk, sir," he said. "If you can find the man, find him, and let me know when you have done it."

"Certainly," said Pitman, stepping over and turning the key in the door. "I let you know, then, that I have found him!"

"What! where?" shouted Holmes, turning white to his lips and glancing about him like a rat in a trap.

"Oh, it won't do -- really it won't," said Pitman suavely. "There is no possible getting out of it, Mr. Holmes. It is quite too transparent, and it was a very bad compliment when you said that it was impossible for me to solve so simple a question. That's right! Sit down and let us talk it over."

Holmes collapsed into a chair, with a ghastly face and a glitter of moisture on his brow. "It -- it's not actionable," he stammered.

"I am very much afraid that it is not. But between ourselves, Holmes, it was as cruel and selfish and heartless a trick in a petty way as ever came before me. Now, let me just run over the course of events, and you will contradict me if I go wrong."

Holmes sat huddled up in his chair, with his head sunk upon his breast, like one who is utterly crushed. "It was only an expedient at first," groaned he. "I never thought that she would have been so carried away."

"Very likely not. However that may be, the young lady was very decidedly carried away, and, having quite made up her mind that her suitor loved her, the suspicion of treachery never for an instant entered her mind. She was flattered by the plumber's attentions. Then Mr. Escott began to call, for it was obvious that the matter should be pushed as far as it would go if useful information were to be gathered. There were meetings, and an engagement, which would finally secure the girl's affections from turning towards anyone else. But the deception could not be kept up forever. So it ended in cruel abandonment."

"It may be so, or it may not, Mr. Pitman," said Holmes, "but if you are so very sharp you ought to be sharp enough to know that it is you who are breaking the law now, and not I. I have done nothing actionable from the first, but as long as you keep that door locked you lay yourself open to an action for assault and illegal constraint."