E-mails Murder by Paul Zindel

This third book in the series finds P. C. and his partner, Mackenzie Riggs, accompanying Mac's father to Monaco where he will speak at the International Psychiatric Association Conference. Although the teens have quite a reputation for solving crimes at home, Dr. Riggs recommends that they see the sights and relax on the beach during this trip. Meantime, one of his colleagues, Prof Marie Harper, is murdered in their hotel. The clues point to a notorious serial killer in France, nicknamed Cyrano. The style of Cyrano was always killed the red haired lady. The two amateur detectives meet Juliet, the inspector's teenaged daughter at the crime scene and the young people begin their own investigation. While the murder has been staged to look like the work of Cyrano, the trio is convinced that the clues and motives point to a different killer. Their personal safety becomes threatened in their quest to solve the thrilling mystery. The suspense and pace will keep readers turning pages. The trio try to solve the modus operandi by reading the e-mails from the serial killer. All the e-mail was written in red ink.
Finally, it turned the killer is Maurice Bourdain a.k.a Prof. Paul Harper. Paul wanted to copy cat the serial killer Cyrano. He booked her wife to the saloon to dye her hair became red.