Here is the second installment in our synopsis of Harry Potter and the Half-Blood Prince, the sixth book in the series — your essential cheat-sheet for diving into the seventh and final book, Harry Potter and the Deathly Hallows. See the first five chapters summarized here.
Chapter 6 - Draco's Detour
Harry is having a lovely time spending his days playing Quidditch and eating delicious food at the Weasley's. He celebrates his 16th birthday, but there is a lot of bad news floating around about disappearances (including those of Florean Fortescue and Ollivander). Everyone receives their official Hogwarts letters containing their school supply list, etc. Harry finds out he is captain of the Quidditch team this year. The children all plan their trip to Diagon Alley but this time they will be driven there by Ministry issued limos and accompanied by Aurors due to the high security measures placed on Harry. Soon they meet Hagrid and there is much rejoicing. They enter Diagon Alley and realize things have changed a lot. The Leaky Cauldron is empty, there are Ministry security posters everywhere, and a bunch of shops have closed down. Some stores and street vendors are selling all sorts of "protection" amulets and other such charms and talismans. Anyway, Harry, Hermione, Ron, and Hagrid go to Madame Malkins to get some robes while everyone else goes to Flourish and Blotts. There they encounter Draco, who is getting fitted for his robes and is irritated that his mother is with him. A confrontation takes place between Harry, Ron, Draco, and his mum Narcissa. Madame Malkin is adjusting the left arm of Draco's robe when he abruptly jerks his arm away, and claims she is poking him with her pins. He throws the robes off and storms out with his mum.
The trio next decide to go see Fred and George's new shop, Weasleys' Wizard Wheezes, which is a huge success. They sell all sorts of joke items (stuff they've invented, muggle magic tricks, etc.) and tell Harry he can take whatever he wants free of charge (after all, Harry gave his TriWizard tournament winnings to them as seed money for the store). Apparently the Ministry has been purchasing all these hex-repelling items from them. Fred and George start grilling Ginny about her flirtatious behavior (rumors they've heard from Ron). The group notices Draco running off somewhere and decide to follow him under Harry's Invisibility Cloak. They follow him to Borgin and Burkes in Knockturn Alley. Draco is yelling at Borgin about repairing something (perhaps one of a pair of something), and threatens him with a visit from Fenrir Greyback (the rather frightening werewolf who turned Remus Lupin into a werewolf). Draco points to something that he wants Borgin to hold onto for him, and shows Borgin something which seems to scare Borgin. Draco leaves the shop, leaving Harry and and friends confused and wanting to find out what Borgin is keeping for Draco. Hermione goes into the shop as a ploy: she admires a necklace and asks Borgin what Draco was looking at because she wants to get him a present. Borgin tells her to get out.
Chapter 7 - The Slug Club
Harry is obsessing about Draco's visit to Borgin's and trying to figure it all out. Hermione and Ron are tired of discussing the issue, but remain supportive and indulge Harry's curiosity. Harry thinks that 1) Draco is trying to get something repaired that is one of a pair and 2) Draco has replaced his father as a Death Eater which is why he didn't want Madame Malkin looking at his left arm (he might have the Dark Mark ). Ron and Hermione don't share the same enthusiasm for his theories. They prepare to go to the school and once again, Ministry-issued vehicles come pick them up. Before he boards the train, Harry tells Mr. Weasley his theory. Mr. Weasley also hesitates to believe it all, but reluctantly promises Harry that he'll look into the matter. Ron and Hermione head to the prefect cars so Harry ends up sitting with Neville Longbottom and Luna Lovegood. They reminisce about their time in the Ministry as Dumbledore's Army fighting the Death Eaters the previous spring. Harry and Neville receive an invitation from Professor Slughorn inviting them to eat lunch with him. They head off and discover that other students including Blaise Zabini (Slytherin), Cormac McLaggen (Gryffindor), Ginny Weasley, and Marcus Belby (Ravenclaw) are there too. The only thing these individuals have in common is that Slughorn had taught their parents/relatives who were in his favorites club (the Slug Club) except for Ginny who impressed him with a Bat-Bogey hex she performed. Eventually, they disperse and Harry, wearing his invisibility cloak, follows Zabini back to his train car so he can snoop on Draco. He hops onto the luggage rack in Draco's train car and listens in on the conversation. Draco mentions that he doesn't really care about school, that he is moving on to bigger and better things, and that he has a task he needs to complete for the Dark Lord. When the train stops, Draco suddenly turns to the luggage rack and stuns Harry, who falls to the floor incapable of moving; Draco knew he was there all along. He stomps on Harry's face and breaks his nose, then covers him with the Invisibility Cloak so that no one will notice him. The train starts moving again and Harry is stuck.
Chapter 8 - Snape Victorious
Harry is angry and panicked on the train. Thankfully Tonks finds him, heals his nose and takes him back to the castle. Snape meets them at the entrance and gives them a hard time. Harry goes to the great hall and sits down next to Ron and Hermione and tells them what happened. Dumbledore starts to make his announcements. He still has his black arm. He announces the appointment of Slughorn as Potions instructor, and Snape will be teaching Defense Against the Dark Arts (DADA). Everyone is shocked and concerned, including Harry. Dumbledore also mentions that the castle has been fortified with all sorts of enchantments to enhance the protection of the school. Hagrid greets the children on their way out of the great hall, mentions that he moved his brother Grawp to a cave nearby, and that he'll see them in class at Care for Magical Creatures. After he walks away, Harry, Ron, Hermione realize that none of them are taking Hagrid's course for N.E.W.T. level and know that will disappoint him.
Chapter 9 - The Half-Blood Prince
The next morning, McGonagall sorts out their new class schedules. Hermione is basically taking every single difficult subject at Hogwarts. It turns out Slughorn will let Harry take his N.E.W.T. level Potions class despite his E grade. Harry and Ron go to Defense Against the Dark Arts with Snape and it's all stressful and tense (basically like it was in Snape's Potions class). They must learn how to cast spells without speaking, which proves incredibly difficult. Snape has them practice casting and blocking hexes nonverbally, and decide to make an example of Harry. Snape nonverbally casts a spell, but Harry instinctively blocks it (verbally though) and it knocks Snape to the ground. Snape is pissed and gives Harry Saturday night detention... but after class Harry hears from Dumbledore that their first lesson is Saturday night, postponing Snape detention! Next is Potions class with Slughorn. Harry and Ron don't have their Potions supplies so Slughorn lends them textbooks and scales. Slughorn quizzes the class on a variety of potions he's made, and Hermione impresses as usual. Slughorn challenges the students to make the Draught of Living Death from the recipes in their books, offering the person who does best a vial of Felix Felicis, a potion that gives good luck for a few days (not allowed on test or game days!). Everyone gets very excited and they all try really hard. Harry opens his borrowed potions textbook and is at first annoyed that it has tons of notes written all over it, but then he tries following them and and his potion turns out best. Hermione is fuming and feels like Harry's cheating, but Harry is delighted! He notices a little note on the back that says rather cryptically: "This Book is the Property of the Half-Blood Prince."
Chapter 10 - The House of Gaunt
Harry keeps using his annotated Potions textbook and begins to ruminate about who the Half-Blood Prince might be. He goes to his lesson with Dumbledore (arm still black) on Saturday night and learns that he wants to educate Harry on Voldemort's past using the pensieve. They jump into the memory of Bob Ogden, who worked for the Ministry, as he walks towards a dumpy house on the outskirts of a small town. He encounters a nasty-looking man holding a wand and a knife who tells Ogden he is not welcome and curses his nose. Another man, Mr. Gaunt, comes out and yells for Morfin (the first foul-looking fellow) to go back into the house. Ogden fixes his nose and informs Mr. Gaunt that he is there to tell him that Morfin attacked a muggle the night before and there will be a hearing concerning this matter at the Ministry. Mr. Gaunt obviously hates muggles and is glad that Morfin attacked one. Ogden and Mr. Gaunt enter the rundown house. Morfin is sitting on the floor conversing in Parseltongue with a snake. Gaunt's daughter Merope is there as well, looking timid and frightened. Gaunt begins raving and waving a black ring around, saying he is above the law because he is the decendent of Salazar Slytherin, and grabs Merope's locket to show off the family crest. When Ogden says Gaunt is not about the law he accuses Ogden of being a muggle-lover. From inside they hear the very handsome Tom Riddle passing by, and it is revealed that he is the man Morfin attacked because of Merope's infatuation with him. Merope gets very frightened and denies everything. Gaunt becomes enraged that Merope dares to fancy a muggle. Ogden helps defend Merope from Gaunt and eventually runs away.
Harry and Dumbledore leave the memory. Dumbledore informs Harry that Merope did survive. Ogden had returned to the house minutes later with reinforcements from the Ministry. Morfin was sentenced to three years of prison is Azkanban and Gaunt, six months. Gaunt (first name Marvolo) is the grandfather of Voldemort while Merope is Voldemort's mother. Along with Morfin they were the last of the ancient wizarding family. The Gaunt family was known for their violence and mental instability. They also married into the family to maintain a pure blood line and squandered all their money due to excessive spending, hence the poverty in which Marvolo and his children lived. Tom Riddle, the muggle whom Merope fancied, is Voldemort's father (recall from Book II). Riddle never would have loved a girl like Merope so she used a love potion to seduce him and they ran off together. Marvolo returned after his six months in prison to find his house empty and that Merope had eloped with Tom. He died before Morfin finished his prison sentence. Tom eventually came back to town with out Merope and claims that she hoodwinked him. Merope probably couldn't bear the thought of constantly giving Tom love potion and hoped that her being pregnant would keep him around or that after all this time he would have fallen in love with her; unfortunately, he did not care and left. Merope eventually died. Dumbledore and Harry finish up and on his way out Harry notices that Dumbledore has the black ring that Marvolo was waving around. Harry inquires and Dumbledore confirms that the ring is the same from Ogden's memory. In fact Dumbledore had acquired it a few days before he fetched Harry from the Dursley's - around the time he had injured his black arm.
See Chapters 1-5 here.