Throughout the sixth “Harry Potter” book, subtitled “Half-Blood Prince,” Harry takes secret evening lessons with Hogwarts headmaster and formidable wizard Albus Dumbledore (played in the films by both Richard Harris and Michael Gambon) as the two try to discover what Voldemort’s gameplan really was all along. Eventually, they discover that the Dark Lord has split his soul a whopping seven times to basically ensure immortality and hidden those bits of soul in various important objects around the wizarding world, which is, obviously, not great. The way the two discern this, though, is through multiple memories Dumbledore and Harry collect from people who knew Voldemort, and only two of these extremely important memories make it into the movies.
One that’s left out is actually from before Voldemort himself is even born, and that memory concerns the Gaunt family, who don’t appear in the movies at all — so if you haven’t read the books, let me break this down for you. Not far from the village of Little Hangleton, the home of Voldemort’s wealthy and handsome Muggle father Tom Riddle, you can find the Gaunt family’s rundown home, where patriarch Marvolo and his children Merope and Morfin live. Thanks to a memory from a Ministry official investigating the Gaunts for misuse of magic, Harry and Dumbledore learn some key facts. Not only are the Gaunts descended from Salazar Slytherin, an original (and evil) Hogwarts founder, but he possesses two items that go on to become Horcruxes: a locket that once belonged to Slytherin and a ring that grievously injuries Dumbledore and turns out to be home to the Resurrection Stone, one of the Deathly Hallows.
The other important thing about the Gaunts is that Merope is in love with the young Tom Riddle and ends up brewing a love potion to ensnare him. She weans him off it after she gets pregnant, hoping he’ll still love her without it, but instead he leaves her. A desperate and heartbroken Merope gives birth to a baby boy on the doorsteps of an orphanage. That baby, also named Tom Riddle, grows up to become Voldemort. Yes, this memory would have been a departure in the movie, but it does provide very crucial Voldemort lore, so it’s a shame that it was cut.