In Potions class, Professor Slughorn assigns students to brew antidotes to poisons, which excites Hermione because Harry won't be able to get help from the Half-Blood Prince.

Without the help of the Half-Blood Prince, Harry is unsuccessful in brewing an antidote to his poison. However, at the end of the lesson, he presents Slughorn with a bezoar instead - delighting Slughorn and infuriating both Ron and Hermione.

After Potions class, Harry stays back to ask Slughorn about Horcruxes - but Slughorn gets upset and storms off.

Harry tells Ron and Hermione about his failure to retrieve the memory from Slughorn, but they are unsympathetic thanks to his triumph with the bezoar in Potions class.

The sixth years have their first [Apparition] lesson with [Wilkie Twycross] in the Great Hall. Harry overhears Draco arguing with Crabbe, but other than that and Susan Bones's [splinching], nothing interesting happens.

After overhearing Malfoy and Crabbe during [Apparition] lessons, Harry is convinced that Malfoy is using Crabbe and Goyle as lookouts - but he doesn't know for what - and he and Ron run up to their [dormitory] to look for them on the Marauder's Map.