Sequel to Harry Potter and the Veil of Memories. Thirteen years after the death of Voldemort, Harry Potter and Ginny Weasley have moved beyond the nightmares of their past. But now the new problems of the world around them threaten to encroach on their harmony: their daughter Siosia is sorted into Slytherin; their best friends Ron and Hermione go through marital strife; and their niece Caroline becomes embroiled in a twisted new version of the DA. But worse than all this, a shadowy, unseen enemy has emerged, one that could threaten the fate of the wizarding world itself.

While Harry and Ginny ponder their many troubles, Caroline finds herself persuaded by a mysterious stranger to re-start the D.A. But what does the stranger really want and what does it have to do with the mysterious chalice, whose history is finally revealed?

Harry remains skeptical that Slughorn is the best choice to take over Dumbledore's position on the island; Siosia and her friends decide to investigate the mysterious Professor Derius.

Caroline continues to have her doubts about Professor Derius, Ginny runs into an old friend, and Remus leads Harry to meet the second candidate to take over Dumbledore's island - the very last person he would have expected.