Here are the July Miniquiz answers.
1] What is the connection between Septimus Winner and Prudence Cowley?
It is Agatha Christie:
Septimus Winner in 1864 wrote the song Ten Little Indians which was one title of the Christie novel that eventually became And Then There Were One.
Prudence Cowley was the maiden name of Tuppence Beresford. Agatha Christie wrote four novels and sixteen short stories featuring Tommy and Tuppence Beresford. Tuppence was played in a brilliantly cast 1983 television series by the fragrant Francesca Annis.
2] The boy has a talent for going underground or even underwater, but follows the game. Five hidden books.
They were the series of books by Patricia Highsmith featuring Tom Ripley.
The Talented Mr Ripley 1955
Ripley Underground 1970
Ripley's Game 1974
The Boy who Followed Ripley 1980
Ripley Underwater 1991
Thanks to all those who entered and especially for the correct or very nearly correct answers that came from Belize, Denmark, Scotland [Edinburgh] and Virginia.