Ninetto De Terenzi is a Roman who lives for the day, helping a lawyer in his intrigues and acting as a stunt double for a cheating engineer; he disapproves of the relationship his widowed mother has with a married man and is engaged to a good worker, whom she tries to betray.

When a rich uncle dies, giving him a great inheritance, Franco will clash with other grandchildren and lawyers.

An alien vessel manages to break the earth defense systems. Captain Layton is sent to investigate and find the invaders. Together with friends from the planet Ganymed he discovers the enemies in a hidden underground city on earth.