The rise and fall of the notorious Roman Emperor Caligula, showing the violent methods that he employs to gain the throne, and the subsequent insanity of his reign - he gives his horse political office and humiliates and executes anyone who even slightly displeases him. He also sleeps with his sister, organises elaborate orgies and embarks on a fruitless invasion of Britain before meeting an appropriate end. There are various versions of the film, ranging from the heavily truncated 90-minute version to the legendary 160-minute hardcore version which leaves nothing to the imagination (though the hardcore scenes were inserted later and do not involve the main cast members).