Dieter von Schwesterkrank is a fashion photrapher in Paris, France.
In 2006, Nancy goes to pick up photos from him and ends up developing them. Later, she sees Dieter at the park studying Noisette Tornade and scares him off, as he doesn't want anyone to know that his great uncle, Hans von Schwesterkrank, was Noisette's Nazi boyfriend. Dieter drops an obituary of Noisette as well as a clock-like puzzle piece, starting Nancy's research on Noisette.
Dieter eventually confesses that he was looking for the treasure Noisette supposedly hid during the war, which is why he started dating Minette, as she owned the windmill Noisette used to live in. However, when she broke up with him, she was all he was interested in.
Apparently Dieter's building used to belong to Hans, as the puzzle piece he had opened up a secret passageway that contained clues Noisette had left.
- In Secrets Can Kill: Remastered Dieter's book called The Photographer's Handbook can be found through the library's search engine.