Percy Jackson is having nightmares about a cyclops chasing Grover Underwood. At school, a group of Laistrygonian giants attack Percy, but he is saved by his half-brother Tyson (a cyclops disguised as a human). Annabeth takes Percy and Tyson to Camp Half-Blood, but they arrive to find the camp under attack by two bronze Colchis bulls. Thalia's tree has been poisoned, leaving the camp vulnerable to enemy attacks. After Clarisse la Rue and Tyson defeat the bulls, Chiron is suspected of poisoning the tree (largely because of his familial connection to the titan Kronos) and is fired from the camp. Tantalus is brought from his prison in Tartarus to be Chiron's replacement.