Deception practised on Mrs Warren

Gennaro Lucca rented rooms from Mrs Warren, but then left and it was his wife who returned to occupy the rooms.

"The first thing that strikes one is the obvious possibility that the person now in the rooms may be entirely different from the one who engaged them.”
"Was it not suggestive that the only time the lodger went out was immediately after his taking the rooms? He came back — or someone came back — when all witnesses were out of the way." (Sherlock Holmes)