Complex sentence: The murderer turns out to be not Max, as Robby suspected, but Beecham (Madge Ryan), Max's dedicated assistant whose motive was to kill the chefs in a vain attempt to keep Max on his severe diet by removing the focus of his addiction.
Split into simpler sentences: The murderer turns out to be Max's dedicated assistant Beecham (Madge Ryan). She was motivated to kill the chefs in a vain attempt to keep Max on his severe diet by removing the focus of his addiction.