Complex sentence: Harry accompanies Albus Dumbledore from Surbiton to the village of Budleigh Babberton to visit former Potions professor Horace Slughorn, who has gone into hiding, but agrees to return to teach at Hogwarts.
Split into simpler sentences: Harry accompanies Albus Dumbledore from Surbiton to the village of Budleigh Babberton to visit former Potions professor Horace Slughorn. Professor Slughorn has been in hiding but agrees to return to teach at Hogwarts.