The House of Hades is the continuation of that damned cliffhanger in The Mark of Athena. Together, Annabeth and Percy must battle their way through Tartarus to locate the Doors of Death and seal it while the rest of the group must go to the House of Hades in the mortal side and seal the door there too. The question is, if they sealed both sides, how can Annabeth and Percy escape?They know the plan is flawed but they have no choice. If they don't seal the Doors of Death Gaea's minions will never die and all attempt to stop them from raising Gaea will be pointless. To top it all, the Romans are on their way to Camp Half-blood to start a war. Needless to say, they must succeed or else.
The story is told by the seven demigods alternating between the group left in the Mediterranean and the pair in Tartarus. This is the ultimate test of courage, strength and determination. The stakes are even higher and sacrifices are made by the most unlikely characters in this fourth book of The Heroes of Olympus Series by Rick Riordan.