The first crime was the apparent suicide of a young man named Mark. Cordelia began the investigation by asking Mark's friends questions about him and his supposed mental state. All of his friends try to convince Cordelia that the suicide was exactly that, a suicide. Cordelia is not convinced and decides to move in to where Mark was living in order to get a better grasp of what could have caused Mark to kill himself. The more Cordelia understands about Mark, the more she is convinced that foul play occurred. Close examination of photos taken of Mark's death reveal to her that Mark could not have killed himself in the way that "witnesses" say. Eventually Cordelia learns that Mark's supposed father could not possibly be his father (blood groups don't match). She confronts Sir Ronald with her evidence and he eventually confesses to the crime. Case solved.