Edgar Wallace credit

It was released and is still shown in Germany as part of the popular German Edgar Wallace film series, and is said to be inspired by his novels (well...).

The same goes for "What Have You Done to Solange?" which is also counted as part of the film series and it is claimed that it is loosely based on the Edgar Wallace novel "The Clue of the New Pin", which is absolute rubbish, as I have read the novel and seen the film and can tell you that they've got absolutely nothing in common, except that there's a pin in the film, but used for very different things. In the book it is a clues as to how the murder was committed and in the film it is something which connects the victims. The book is about a rich man being found murdered in a locked vault, the main character doesn't know that his friend is the murderer, until the both fall in love with the same woman and the murderer gets jealous of his friend. In the movie a bunch of catholic school girls get murdered because of something they've done and one of their teachers (who had an affair with one of the girls and shortly became a suspect) tries to solve the case.

Personally I wouldn't call either of them them Edgar Wallace movies.