The grandson is feeling unwell and his grandfather comes to visit to cheer him up bringing a book with him (much to the grandson's disdain).
But this is a special book. The story contains fencing, fighting, revenge, true love, pirates, giants, miracles, captures, escapes etc.
In the country of Florin, Westley and Buttercup fall in love but as he is poor, he sets off to earn some money so they can get married. But woe is me. His ship is attacked by the Dread Pirate Roberts, who never leaves captives alive.
Crown Prince Humperdinck decides to marry Buttercup (and in the spirit of all good fairy tales, she has no choice - the law gives him the right to choose his bride, no questions asked).
Shortly before the wedding, the future Princess is kidnapped by a short guy with an even shorter temper from Sicily, a giant from Greenland and a former alcoholic Spaniard (incidentally, the Spaniard is a master sword fighter who is set on avenging his father who was murdered by the Six Fingered Man).
The kidnappers make off with their prey but are followed by The MIB (Man in Black).
He catches up, knocks the Spaniard unconscious in a duel, beats the giant in hand to hand combat, wins a battle of wits against the short Sicilian guy and kidnaps Buttercup himself.
By this time, Prince Humperdinck and his partner-in-crime, Count Rugen, are tailing them hoping to snatch the girl back.
The MIB turns out to be the Dread Pirate Roberts aka Westley!! The previous Roberts (who wasn't actually Roberts, but a sailor called Cummerbund) decided to retire and hand the name over to someone else.
The reunited pair escape into the Fireswamp and are faced with the three terrors: The Flame Spurt, Lightening Sand and R.O.U.Ses (Rodents Of Unusual Size). They are caught on the other side of the swamp and Buttercup negotiates the safe return of Westley to his ship if she agrees to return to Florin.
The Prince instructs the Count (did I tell you the Count is the Six Fingered Man?) to take Westley and throw him into the Pit of Despair. It turns out that the Count is at present writing a definitive work on his deep and abiding interest. Pain. So he uses The Machine, his marvellous invention based on the concept of the suction pump, to suck one year of Westley's life away.
Buttercup tells the Prince that 1. she loves Westley and 2. she thinks the Prince is nothing but a coward with a heart full of fear. Now, the Prince is not particularly happy about this and rushes off to the Pit of Despair and turns The Machine on, sucking 50 years away.
Oh, before I forget, Spaniard and Giant have met up again and are looking for the MIB to help with the revenge part of the story. They track him down to the Pit of Despair and find Westley is Mostly Dead.
They go to see Miracle Max who retired after being fired by the King's stinking son but on hearing that Westley is Buttercup's true love makes a chocolate coated miracle pill (apparently the chocolate coating makes it go down easier) to bring him back to life.
The pill works and the Spaniard, the Giant and the revived but still really weak Westley storm the castle.
The Spaniard finds and kills the Six Fingered Man, Buttercup ties the Prince to a chair, the Giant finds 4 white horses, Westley offers the job of Dread Pirate Roberts to the now unemployed Spaniard and they all ride off to freedom.