Summary:

Percy Jackson and Harry Potter's worlds collide when a mysterious Time-Turner teleports the characters to Camp Half-Blood - and for a good reason: Calypso has been captured by Khione! Now, Harry, Ron, Hermione, Ginny, Luna, Neville, Draco, Astoria, Percy, Annabeth, Nico, Leo, and Will must face one of the most difficult challenges they've faced yet: Khione's labyrinth! The labyrinth is full of twists and turns, nasty surprises and creatures that can drive a person to insanity. You'll have to read to see if they make it out alive - or become statues of ice in the snow goddess's home. (During Half-Blood Prince, after Trials of Apollo series.)