Complex sentence: Ventura realises that Einhorn is in fact Finkle, having undergone surgery to change his gender, murdered the hiker, and took on her identity to get revenge on the Dolphins.
Split into simpler sentences: Ventura realises that Einhorn is in fact Finkle, having undergone surgery to disguise himself as the missing female hiker he possibly murdered. Then taking on her identity to get revenge on the Dolphins.