Harry Potter and the Half-Blood Prince
Chapter 18 - Birthday Surprises
Remembering Dumbledore′s order Harry tries to get the true memory from Slughorn during the Potions lesson. But Slughorn refuses to talk to him about this topic.
Later in February all sixth-years have their first Apparition lesson, which isn′t very successful for the students. At his seventeenth birthday Ron falls victim to a love potion which was actually meant for Harry. Harry brings Ron to Slughorn, who gives him an antidote.
Slughorn has a barrel of mead which he should have given to Dumbledore, but Slughorn had decided otherwise. He invites Ron and Harry to drink the mead with him. Ron is the first one to drink it and gets poisoned by the mead.