The crime fiction series’ title CLUE is formed by the initials of the four main characters in the series: Cecilia, Leo, Une and Egon the dog. The CLUE-books are modern, realistic and action packed-books. The series consists of 13 titles.

The plot is based in and around «The Pearl» in Ship Bay. In each of the series’ books a new mystery and a new ethical question is introduced along with the thoughts of one of the world’s most well-known philosophers. The CLUE books are best selling crime fiction for younger readers aged 9-12.