Dumbledore schedules private lessons with Harry at the beginning of the school year, and they use their newfound time together to take trips into Dumbledore’s Pensieve, a stone basin that acts as a gateway into other people’s memories. Dumbledore retrieves the memories from his subjects and stores them in small crystal vials. When Dumbledore pours the contents into the Pensieve, he and Harry can fall face first into the basin and be magically transported to the time and place of the collected memory, where they will watch it transpire from the sidelines. Dumbledore first introduced Harry to the Pensieve in Book V of the series, Harry Potter and the Order of the Phoenix, and the Pensieve continues to play a pivotal role in Book VI. Now, Dumbledore has collected memories from Bob Ogden, who worked for the Department of Magical Law Enforcement; Caractacus Burke, of Borgin and Burkes; Morfin, Voldemort’s uncle; Professor Horace Slughorn; Hokey the House Elf; and several of his own memories, all designed to give Harry a better sense of Voldemort’s past and his reoccurring tendencies. From these, Harry learns that Voldemort often steals objects that don’t belong to him. Voldemort stole his housemates’ things at the orphanage, and then later, after murdering Hepzibah Smith, he takes Slytherin’s locket and Hufflepuff’s cup. Harry also learns that Voldemort will kill for revenge as well as gain, and that he feels an unusual tie to Hogwarts, trying, on several occasions, to secure a teaching job at the school. Voldemort is also extremely self-sufficient, denying Dumbledore’s offer to help him gather his schoolbooks and prepare for Hogwarts, and is often excited by the prospect of being unordinary, whether by learning he is a wizard or changing his name from Tom to Voldemort.

When Ron runs into his little sister Ginny kissing her boyfriend Dean Thomas in the Gryffindor common room, he gets extraordinarily angry. Ginny, defensive and annoyed, accuses Ron of never having kissed a girl, even though his friends have both done so already (Harry has kissed Cho Chang and Hermione has kissed Victor Krum.) Ron is mad and embarrassed, and asks Harry if it’s true that Hermione kissed Victor. Harry tells Ron he doesn’t know, even though the answer is yes. Ron’s anger gives way to jealousy, and he begins ignoring Hermione. Not long after, Ron starts kissing Lavender Brown, which enrages Hermione and further widens the gap between them. For Harry, all of this tension is extremely troubling. Although he hates to see his friends fighting, he is also frightened of what might happen were they to get together and start dating. Harry fears that they would either start fawning all over each other all day long, like Bill Weasley and his fiancée Fleur, or they would descend into awkward, non-conversation, which is what happened to Harry and Cho Chang. Regardless, Harry tries to stay out of their disagreements, as he has always done. Finally, when Ron breaks up with Lavender, he and Hermione patch up their differences. At the close of the book, Hermione is curled into Ron’s shoulder, crying and mourning the loss of Dumbledore. It is clear that she and Ron will continue to be close in Book VII.

At the close of the book, Draco Malfoy finds Dumbledore weak and defenseless, without a wand or any kind of support from Harry or the Order of the Phoenix. Draco could easily kill Dumbledore immediately, yet he stalls for several minutes. Even when Dumbledore tells Draco to get on with his mission, he still cannot bring himself to complete the task and simply stares at Dumbledore. Sensing his fear, Dumbledore reminds Draco that he is not a killer, and that killing is never as simple as the innocent believe it to be. Dumbledore senses that Draco is waiting for backup from the Death Eaters fighting below and starts to ask him questions about what he has been up to during the school year. Eventually, Malfoy admits that he is only killing Dumbledore because he fears for the safety of his family, whom Voldemort has threatened should Draco fail at this task. Dumbledore tells Draco that he and Order could protect Draco and his family, faking Draco’s death and shielding them from Voldemort and the Death Eaters, even agreeing to protect Draco’s father, Lucius Malfoy, after he is released from Azkaban. Eventually, Draco lowers his wand and seems almost ready to accept Dumbledore’s generous offer. At that moment, Snape bursts into the room and, seeing Draco’s inability to perform, casts the spell that kills Dumbledore. Later, after Dumbledore’s funeral, even Harry feels nearly sympathetic toward Draco, whom he does believe would have gone through with the murder had Snape not stepped in.