A Question of Trust by Victor Canning - (Footprints Without Feet - X) - Full Explanation

Victor Canning was a prolific British writer of novels and thrillers who flourished in the 1950s, 1960s and 1970s.It is said that you must set a thief to catch a thief. But it is also said that there is honour among thieves. Which saying does this story illustrate?
The plot is about a man named Horace Danby who is 50 years old and everyone around him thinks he is a good and an honest man. He used to build locks and used to earn enough profit so that he could hire two servants to help him. He was sent to jail once about 15 years ago because he used to commit robberies every year. This year, when he goes to a house for robbery, he meets a woman who pretends to be the owner of the house. Later when he leaves from there and is arrested after 2-3 days, he comes to know the truth of that lady.