https://www.reddit.com/r/AskHistorians/comments/6sfj2v/whatever_happened_to_the_house_dick/dldl01g/
Experience was the most important attribute of a hotel detective, since, for the most part, such men had three main functions to perform. The first was to protect the hotel's reputation and prevent it from unwittingly breaking any laws, which, especially in earlier periods, often involved preventing an establishment from acquiring a reputation as the sort of place that allowed unmarried couples to have sex on the premises - very often an offence at the time under laws relating to "unlawful cohabitation". A 1979 article in Texas Monthly notes that in earlier times a house officer would, as part of his routine, challenge male guests with the line "Is there a woman in your room?" Dev Collans, in I Was A House Detective (1954) describes enlisting bellboys to report on "couples who wouldn't open their suitcases while the bellboy was still in the room; married couples didn't hesitate to. A man in sleek clothes with a woman whose shoes were run down at the heels is another giveaway."