Chapter Summaries

Gavin and Cordelia took Snape’s Potions resit, and Gavin failed while Snape quietly helped Cordelia recover. Gavin then negotiated with Snape to dismantle a Hebridean Black, but went to bed exhausted with the sense that he had forgotten something important.

• Cordelia explained their lateness to Snape, who deducted five Hufflepuff points from Gavin and assigned them potions to brew.
• Snape praised Cordelia’s Cure for Boils and gave her a Restorative Potion, while Gavin’s attempt to brew one earned him a Troll.
• Gavin asked Snape to help dismantle a Hebridean Black, and Snape agreed after inspecting the dragon and its legal documents.
• Snape negotiated for a larger share of the dragon materials and demanded Gavin’s Golden Snitch-catching method, but Gavin offered to help Cordelia become Slytherin’s Seeker instead.
• Gavin and Snape signed a Magical Contract settling the division of the dragon materials after lengthy bargaining.
• Gavin returned to the dormitory exhausted, fell onto his bed, and could not remember what he had forgotten.

Gavin realized the Horcrux diary had disappeared and searched his roommates’ memories, but found no trace of it. With Dumbledore away until around Halloween and unable to be reached, Gavin borrowed the Marauder’s Map to investigate, leaving the diary’s whereabouts unknown.

• Gavin discovered the diary was missing and used Legilimency on Justin and Ernie, finding no evidence that either had taken it.
• Gavin tried to contact Dumbledore, but learned he was away until around Halloween; Nyx could not find him, and Professor McGonagall knew no way to reach him.
• Gavin cooked breakfast for Justin and Ernie, then asked Professor McGonagall where Dumbledore had gone while concealing the diary’s disappearance.
• Gavin rented the Marauder’s Map from Fred Weasley and George, searched for the diary and checked Lockhart’s office, but found no answers.

Gavin watched Lockhart’s first Defense Against the Dark Arts lesson and became convinced the professor had an unsettling interest in Cordelia. When Lockhart invited Cordelia to his office, Gavin warned her away, but she returned after refusing and assured him she trusted him.

• Cordelia gave Gavin a honey sweet from Dibby before they entered Lockhart’s classroom.
• Lockhart released Cornish Pixies during a demonstration, protected the class with a barrier, and expertly subdued them while Draco Malfoy struggled and was humiliated.
• Cordelia performed a precise Freezing Charm and earned ten points for Slytherin, while Gavin noticed Lockhart repeatedly watching her.
• Lockhart invited Cordelia to his office for extra instruction, and Gavin warned her not to go because something was wrong with him.
• Cordelia returned after turning Lockhart down, told Gavin she trusted him, and explained that she had said he did not count as a man.

Gavin investigated the dangers surrounding Lockhart and the Chamber of Secrets, learned how Polyjuice Potion worked, and sealed the Chamber entrance with Dragon-Blood Cement. The chapter ended with Moaning Myrtle seeing something slip into a faucet and screaming that there was a ghost.

• Gavin received Mr. Rowle's reply, which explained that a Thief's Downfall could remove potion disguises and promised support for Cordelia's safety.
• Gavin checked the Marauder's Map and found Lockhart stationary in his office while the Diary and Dumbledore remained missing.
• Snape gave Gavin the processed Black Dragon materials and explained that Polyjuice Potion preserved the drinker's original identity beneath the transformation.
• Gavin used Dragon-Blood Cement to seal the sink's pipe leading to the Chamber of Secrets and placed alert spells on the barrier.
• Moaning Myrtle heard strange noises, saw a dark mass slip into a faucet, and screamed, "There's a ghost!"

Gavin investigated why the Marauder's Map showed Lockhart under his own name, then researched the Basilisk in Newt Scamander's book. Newt's notes led Gavin to improve Muffliato into a sound-blocking spell, and he left the Potions Classroom with Snape's old textbook.

• Gavin realized the Marauder's Map had never shown Peter Pettigrew and considered whether the map concealed certain names, leaving Lockhart's identity unexplained.
• Gavin found Hagrid's 1943 expulsion recorded in a Hogwarts Board of Governors memorandum, then set the record aside and searched for information about Basilisks.
• Gavin discovered that two pages of Newt Scamander's Fantastic Beasts and Where to Find Them had been stuck together, revealing detailed notes about Basilisk behavior and its sensitivity to sound.
• Gavin connected the Basilisk's sensitivity to sound with Mandrakes and went to Snape's Potions classroom to look for a way to protect himself from their cries.
• Gavin found Snape's old Advanced Potion-Making textbook, learned Muffliato from its notes, and modified the spell to cancel out sound.
• Gavin took Snape's textbook and left the classroom, considering whether to ask Snape about the Half-Blood Prince.

Cordelia won Slytherin’s Seeker tryout by catching the Golden Snitch faster than Draco Malfoy, then Malfoy accused Gavin of helping her cheat and insulted Ron. Ron’s spell backfired, and Gavin and Cordelia left to help him while Malfoy threatened to tell his father.

• Gavin asked Colin Creevey to photograph Cordelia catching the Snitch so he could send the pictures to her father.
• Cordelia used Gavin’s trajectory method to catch the Golden Snitch in just over eight minutes and win the Seeker position over Malfoy.
• The Gryffindors arrived and recognized Cordelia’s flight path as similar to Cedric Diggory’s, while Fred and George suspected Gavin had taught her.
• Malfoy accused Gavin of helping Cordelia cheat and called him a Mudblood, so Ron charged in and his slug-vomiting curse rebounded onto himself.
• Gavin and Cordelia mocked Malfoy and helped Harry take Ron to the Hospital Wing.

Gavin visited Hagrid with Cordelia, brought him photographs of Norbert, and asked him to obtain meat, while Ron recovered from his backfired Slug-Vomiting Charm. After Mrs. Norris was found petrified beside a threatening message, Gavin investigated the scene and later grew suspicious of Lockhart after hearing about the new Duelling Club.

• Madam Pomfrey treated Ron for the Slug-Vomiting Charm, and Gavin suggested moving him to Hagrid's Hut so fewer people would see him suffering.
• Gavin and Cordelia visited Hagrid, who was moved by Gavin's photographs of Norbert, and Hagrid agreed to find at least five cows, other meat, and live roosters for Gavin.
• The group discussed Malfoy's insult and Gavin's translated curse, while Hagrid thanked Gavin and promised to help him whenever needed.
• Gavin and Cordelia returned to the castle and found Mrs. Norris petrified beneath a threatening message; Filch accused Susan, but Professor McGonagall restored the cat and began investigating.
• Malfoy blamed Fred and George, but Snape gave Malfoy an alibi and suggested the twins as suspects; Gavin checked the Marauder's Map but found no clues.
• Mr. Rowle told Gavin that the Board of Governors had rejected replacing Lockhart, and Lockhart announced a Duelling Club, prompting Gavin to wonder whether he could have petrified Mrs. Norris.

At Hogwarts' first Duelling Club, Gavin defeated Cordelia and then humiliated Draco Malfoy by precisely cutting apart his clothes with a Severing Charm. The spectacle prompted Snape to ban using the charm on students' clothing, while Harry and Ron asked Gavin what spells they should learn.

• Lockhart opened the Duelling Club with Cordelia and Gavin as his first pair, and Gavin won their duel after evading her spells with sunglasses made by Transfiguration.
• When Malfoy mocked the duel and challenged the pair, Gavin took Cordelia's place and faced him on the platform.
• Malfoy hit a vine with a corrosive spell, and Snape and Lockhart agreed it was not Dark Magic; Gavin responded by using Diffindo to cut Malfoy's robes into pieces without touching him.
• Snape repaired Malfoy's clothes and warned the students against using the Severing Charm on clothing; the next day, the school added a rule banning it.
• Harry asked Gavin for dueling lessons, and Gavin suggested the Disarming Charm for Harry and Parseltongue for Ron.

Gavin investigated the Chamber of Secrets, heard Moaning Myrtle describe a suspicious man near the bathroom, and joined Harry, Ron, Hermione, and Cordelia as they discussed the Heir of Slytherin. He arranged to have Polyjuice Potion brought in by house-elf and recruited Harry and Ron to record Parseltongue, hoping the recordings might reveal a clue.

• Gavin asked Moaning Myrtle what she had heard near the Chamber of Secrets, and she recalled a deep-voiced man muttering about Mudbloods and Dragon Blood.
• Gavin found Hermione, Harry, Ron, and Cordelia brewing Polyjuice Potion and heard that they suspected Draco Malfoy was the Heir of Slytherin.
• Cordelia accused Gavin of being the Heir, but his lack of motive weakened her theory and the others laughed at her deduction.
• Gavin suggested that Cordelia ask her father to buy Polyjuice Potion and have Dibby bring it into Hogwarts, so Cordelia hurried off to write to him.
• Gavin told Harry and Ron that he was investigating the Chamber and asked Harry to record Parseltongue, then let Ron record his own imitation for comparison.

Gavin practiced reshaping the Shield Charm and discovered that the Obscurus could destroy a dragon scale, giving him a possible way to destroy the diary if he found it. As Lockhart kept pursuing Cordelia and McGonagall found no clear evidence of misconduct, Gavin planned to investigate Lockhart by impersonating Cordelia, and persuaded her to give him a strand of hair.

• Gavin refined his Shield Charm and found that the Obscurus consumed a dragon scale, convincing him it could destroy a Horcrux.
• Gavin continued to suspect Ernie might be connected to the diary, but kept Lockhart as his priority as the professor repeatedly sought private meetings with Cordelia.
• Gavin intervened when Lockhart tried to invite Cordelia again, then asked McGonagall for help; she said she saw no concrete evidence of misconduct.
• Dibby delivered disguised bottles from Mr. Rowle, and Gavin showed Cordelia and her friends the package before explaining his plan to investigate Lockhart while disguised as her.
• Gavin used Legilimency to win repeated rounds of rock, paper, scissors, and Cordelia reluctantly gave him a strand of hair for the plan.

Gavin suspected that Justin’s exhaustion and new relationship with Susan might be connected to Tom’s search for a target, while he and Cordelia staged a public falling-out to carry out their plan involving Lockhart. The chapter ended with Gavin transformed into Cordelia and heading to find Lockhart as Cordelia waited under Harry’s Invisibility Cloak.

• Ernie revealed that Justin and Susan had grown close after a Quidditch match, and Justin asked Ernie for more of his supplement.
• Gavin suspected something was wrong with Justin and decided to examine his memories later, but he prioritized meeting Cordelia before Defense Against the Dark Arts.
• After Lockhart’s lesson, Cordelia publicly challenged Gavin to choose between her and Justin, then called Gavin “Mud! Blood!” and ran off as planned.
• Gavin found Cordelia waiting in a classroom, reassured her, and prepared to impersonate her with Polyjuice Potion while she stayed hidden under Harry’s Invisibility Cloak.
• Gavin transformed into Cordelia, and after Cordelia stopped him from touching her body, he left to find Lockhart.

Gavin disguised himself as Cordelia to question Lockhart and investigate his identity, but drinking Polyjuice made him look like an unknown man rather than Lockhart. Afterward, Lockhart revealed that he had identified Cordelia as an Obscurial and intended to fulfill Grindelwald’s work; Justin then arrived with a black diary.

• Gavin disguised himself as Cordelia, used prepared thoughts to fool Lockhart’s Legilimency, and gained entry to his office.
• Gavin questioned Lockhart about his published adventures and the Homorphus Charm, then falsely told him that Hagrid was the Heir of Slytherin.
• Gavin took a strand of Lockhart’s hair during a brief hug, drank Polyjuice Potion, and transformed into an unfamiliar, middle-aged man.
• Lockhart found the Pocket Watch under Cordelia’s chair and celebrated that he had discovered the perfect Obscurial.
• Justin Finch-Fletchley came to Lockhart’s office and offered him a black diary as a Dark Magic Object.

Tom Riddle struggled to escape Justin Finch-Fletchley, whose knowledge and magical defenses convinced Tom he was far more dangerous than he appeared. After breaking through Justin’s Flame-Rune Seal, Tom chose a vulnerable sleeping boy as his next host, but his magic instead drew Justin to the Diary, where Tom began manipulating him again.

• Tom realized Justin’s knowledge, resistance to Dark Magic, and ability to interrupt his attempts to drain life force meant he had to avoid him.
• Tom used his soul’s strength to escape the Diary, then absorbed some of Justin’s Flame Seal magic despite the damage it caused to the Horcrux.
• Tom surveyed the sleeping boys and chose the one with an emotionally wounded, unstable soul as his new host.
• Tom used a magical pulse and Confundus Charm to make Justin take the Diary to an empty classroom.
• Justin opened the Diary and wrote that he wanted the whole school to notice him, and Tom introduced himself as Tom Riddle.

Tom Riddle secretly used Justin as a host, feeding on his life force and the fear spreading through Hogwarts while planning to open the Chamber of Secrets. When Justin broke free and ran to Lockhart with the Diary, Tom abandoned him and considered making Lockhart his next host.

• Tom learned through Justin's memories that his real name was Gavin Gu and that the Wizarding World believed Voldemort had been killed by Harry Potter as a baby.
• Tom hid the Diary in the Muggle Studies section of the library, drained Justin's life force, altered his memories, and used a door-triggered seal to conceal their meetings.
• Tom found the Chamber of Secrets entrance blocked with dragon-blood mud, so he wrote a bloody message on the wall and petrified Mrs. Norris to spread fear at Hogwarts.
• Tom exploited Justin's feelings for Susan Bones and fed on the fear and emotional turmoil spreading through the school, then gained more strength when Justin drank a powerful tonic.
• Justin's strengthened will broke Tom's seals and Confundus Charm, and he ran with the Diary to Lockhart's office.
• Tom decided Justin was no longer a safe host and considered deceiving Lockhart into becoming his next one.

Cyril Rosier reflected on how he had impersonated Gilderoy Lockhart to infiltrate Hogwarts and investigate Cordelia Rowle, whom he believed was a living Obscurial. After confirming his suspicion, he considered using the Chamber of Secrets to create chaos and abduct her.

• Cyril recalled how he had abducted the real Lockhart, concealed him in an enchanted pouch, and taken his identity to enter Hogwarts.
• Cyril explained that years of experiments had failed to produce a stable Obscurial, until he discovered reports about Cordelia Rowle and suspected she had been cured.
• Cyril used Lockhart's position and the Duelling Club to observe Cordelia, while Gavin Gu repeatedly blocked his attempts to get her alone.
• Cyril followed Cordelia after she argued with Gavin, comforted her, and used his Pocket Watch to confirm that she carried an Obscurus.
• Justin brought Cyril a Diary connected to the Chamber of Secrets, and Cyril considered opening the Chamber to cause enough chaos to abduct Cordelia.

Cyril Rosier, posing as Lockhart, questioned Tom Riddle’s Diary and accepted its false claim that Hagrid was behind the Chamber of Secrets attacks. Tom manipulated Cyril into opening the way to the Chamber, while secretly draining his life force, and they descended together to confront the monster.

• Cyril questioned the Diary, and Tom claimed that Hagrid had opened the Chamber of Secrets fifty years earlier and released an acromantula.
• Cyril believed Tom’s story and asked him to help open the Chamber, while Tom sensed Cyril’s greed and agreed to guide him.
• After Cyril left his office, Tom began draining his life force, and Cyril remained unaware as they reached the Second-Floor Bathroom.
• Tom used Parseltongue to open the sink entrance, but Cyril found Dragon-Blood Cement blocking the passage.
• Cyril dissolved the seal with a green liquid, and he and Tom descended into the Chamber of Secrets.

Gavin caught Hermione trying to infiltrate the Slytherin Common Room and told her that Hagrid had been suspected of opening the Chamber of Secrets. Justin then confessed that Tom’s Diary had influenced him and that he had handed it to Lockhart; Gavin discovered the Chamber had now been opened and sent Hermione and Justin to warn the school while he ran to the entrance.

• Gavin helped Hermione hide the unconscious Millicent Bulstrode, then learned Hermione planned to impersonate her and question Malfoy about the Chamber of Secrets.
• Gavin told Hermione that Hagrid had been named a suspect when the Chamber was opened fifty years earlier, prompting her to abandon her plan and go ask Hagrid about it.
• Justin confessed that Tom’s Diary had influenced him, and that he had given the Diary to Professor Lockhart after regaining his memories in the library.
• Gavin used Legilimency on Justin and confirmed the Diary had affected his memories and actions; he then revealed that he was already a doctoral student at Oxford, easing Justin’s jealousy.
• Gavin sensed that someone had broken through the dragon-blood cement and concluded the Chamber of Secrets had been opened, ordering Hermione to alert Professor McGonagall and Justin to warn students.
• Gavin told Hermione that the entrance was in the Second-Floor Bathroom and ran there himself, determined to keep others out of danger.

Cyril entered Slytherin’s Chamber of Secrets under the Diary’s influence, mistook the Basilisk for an Acromantula, and was killed after his protective artifacts failed. Tom Riddle formed a temporary body, but Gavin Gu appeared and took the Diary, while another figure awakened in a Hogsmeade cellar and vowed to continue.

• Cyril opened the Chamber of Secrets and released the Basilisk after Tom Riddle used Parseltongue to command it.
• The Basilisk’s gaze destroyed Cyril’s protective artifacts, and it crushed him while Tom explained how the Horcrux had intensified his greed.
• Tom absorbed Cyril’s remaining life force, emerged from the Diary in a temporary body, and picked up Cyril’s wand.
• Gavin Gu appeared from behind a pillar, silenced the Main Hall, and took the Diary before Tom could retrieve it.
• Tom recognized Gavin Gu and confronted him as someone in a Hogsmeade cellar awoke and vowed to remember Tom and keep pursuing Obscurus and Cordelia.

Gavin fought Tom Riddle and the Basilisk in the Chamber of Secrets, using spells, Dungbombs, and his Obscurus to turn the battle around. He destroyed Tom and the Diary, then faced the Basilisk as it kept its distance from him.

• Tom ordered the Basilisk to kill Gavin, but Gavin silenced him with Muffliato and attacked with transfigured ice blades.
• Gavin drove the Basilisk away with Dungbomb Max Plus Pro Ultra 3.0 and wore Tom down with spells until he disarmed him.
• Tom disarmed and petrified Gavin, then revealed that the Horcrux had absorbed the Flame Seal and tried to use the Cruciatus Curse.
• Gavin used his protective Shield Charm and Obscurus to escape the trap, scare off the Basilisk, and destroy the Diary, killing Tom's soul fragment.
• Gavin turned toward the Basilisk, which remained wary of the Obscurus, and told it that it was next.

Gavin fed the Basilisk, sent it back to sleep, and confirmed that Tom and Fake Lockhart were gone, though many questions remained unanswered. As he left the Chamber of Secrets, Cordelia confronted him after he broke his promise to find her within two hours.

• Gavin cleaned the Chamber of Secrets, fed the Basilisk five cows, and used recorded Parseltongue to send it back into the Slytherin Statue.
• Gavin closed the statue's mouth and discovered that Tom's Diary and Fake Lockhart had been destroyed, while the real Lockhart was alive and unconscious in an enchanted bag.
• Gavin searched Fake Lockhart's belongings and recognized the Flame Crest he had found inside the Black Dragon as a possible link to Tom's Flame-Rune Seal.
• Gavin headed for the exit, planning to eat and rest, but remembered that he had promised Cordelia he would find her within two hours.
• Gavin opened the Chamber's door and found Cordelia waiting with her Wand and Nimbus 2000 after three hours had passed.