The Titan's Curse (Book Three, Percy Jackson and The Olympians Series)

 It is winter, and the Titan Lord Kronos' power is growing immensely. Meanwhile, Percy, along with Annabeth, Grover and Thalia, is sent to recruit two kids that are suspected of being Half-Bloods. However, the mission goes horribly wrong and Annabeth plunges 500 feet down the side of a cliff. Believing her to be dead, the whole of Camp Half-Blood is distraught. One night, Percy has a dream of Annabeth and the Goddess Artemis chained to the ground, holding up an immense weight. Accompanied by his friends, Thalia and Grover, as well as their new found allies, the Hunters of Artemis, Percy sets out to rescue her and the goddess Artemis. The journey is long, unrelenting, and filled with friends and foes alike, but Percy is determined to rescue his friend.

Riordan weaves a story filled with despair, hope, monsters and gods that all ages will enjoy. This third installment gives backstory on Riptide's past. It is also loosely based on the Tasks of Hercules.