When Horace was tricked by the lady thief and was caught,he became an assistant librarian in prison as he used to steal money only to buy books also he steal only from the rich peoples n he steal only once in a year,this was how he became an assistant librarian in a prison.

Horace Danby became an assistant librarian in the prison in the short story "A Question of Trust" by P.G. Wodehouse. The story is about a middle-aged man who is a skilled thief and is caught stealing a valuable necklace from a wealthy woman's house. He is sentenced to three years in prison, where he befriends the prison librarian, Mr. Mulliner. Here are the details of how Horace Danby becomes an assistant librarian in the prison:

First Meeting with Mr. Mulliner
- Horace Danby meets Mr. Mulliner, the prison librarian, when he is sent to the library to do some research for his appeal.
- Mr. Mulliner is impressed with Horace's knowledge of literature and his ability to find the information he needs quickly.

Offer of a Job
- After a few more visits to the library, Mr. Mulliner offers Horace a job as his assistant librarian.
- Horace is initially hesitant, as he doesn't want to be seen as a snitch or a "screw-lover" by the other prisoners.
- However, Mr. Mulliner assures him that the job is legitimate and won't cause any problems.

Training and Duties
- Horace undergoes some training to learn how to catalog and organize books, as well as how to check them in and out to the other prisoners.
- He takes his duties seriously and becomes a valuable member of the library staff.
- He also uses his access to the library to do some research on the necklace he stole, hoping to find a way to return it without being caught.

Trustworthiness
- Horace earns Mr. Mulliner's trust by being reliable, honest, and hardworking.
- Mr. Mulliner even confides in Horace that he is planning to retire soon and hopes that Horace will take over as the prison librarian.
- Horace is touched by this show of trust and decides to come clean about the necklace, returning it to its rightful owner and accepting the consequences of his actions.

In conclusion, Horace Danby becomes an assistant librarian in the prison through his knowledge and skills, his willingness to work hard, and his trustworthiness. His job in the library ultimately leads him to a moral reckoning and a chance for redemption.