The Mark of Athena recap

The Greek warship Argo II reaches Camp Jupiter, and Percy and Annabeth are joyfully reunited. But the fragile peace shatters when Leo, briefly possessed by an evil spirit, fires the ship's weapons on the Roman camp, making the Romans believe the Greeks have attacked. The seven demigods flee, sailing east toward the ancient lands of Rome and Greece to close the Doors of Death and stop Gaea from rising. Annabeth carries a solitary quest handed down from her mother, Athena: to follow the Mark of Athena and recover a long-lost statue that could reconcile the Greek and Roman demigods. The crew battles giants and monsters across the Mediterranean and rescues Nico, who has been captured. In Rome, Annabeth follows the trail alone into an underground lair and confronts the monstrous spider Arachne, recovering the great statue. But as she does, the floor gives way, and she and Percy, refusing to let go of each other, tumble together into Tartarus, the deepest pit of the underworld, leaving their friends to sail on toward the Doors of Death to find them.

Previously: A new Great Prophecy warned of seven demigods facing the primordial earth goddess Gaea, who is waking and raising the giants, ancient enemies of the gods. To force the long-separated Greek and Roman demigod camps to cooperate, the goddess Hera swapped two heroes and erased their memories: the Roman Jason went to the Greek Camp Half-Blood, and the Greek Percy Jackson, son of the sea god, went to the Roman Camp Jupiter. Jason, with the new demigods Piper and Leo, recovered his memory and learned of Gaea's plan, then built a flying warship, the Argo II. Percy, meanwhile, made friends among the Romans, Hazel and Frank, freed the god of death in Alaska, and helped defend Camp Jupiter. As this book opens, the Argo II is carrying Jason, Piper, Leo, and Annabeth to the Roman camp to unite the seven demigods and sail for the ancient lands, where the Doors of Death must be closed before Gaea can fully rise.

Annabeth, following the Mark of Athena alone, tracks the lost Athena Parthenos statue to a hidden cavern beneath Rome and outwits and defeats the ancient spider-creature Arachne who guards it, freeing the statue that could heal the rift between the Greek and Roman camps. But the victory becomes a trap: the ground collapses, and Arachne, ensnared but not dead, drags Annabeth toward a vast chasm that opens into Tartarus, the abyss beneath the underworld. Percy reaches her in time but cannot pull her free, and rather than lose each other, the two choose to fall together into the pit, trusting their friends to find them on the far side. The rest of the crew, Jason, Piper, Leo, Frank, Hazel, and Nico, secure the Athena Parthenos aboard the Argo II and set course for the House of Hades in Greece, where the Doors of Death stand. Their plan is desperate: close the Doors from the mortal world while Percy and Annabeth try to reach them from within Tartarus, so the two can escape and Gaea's path back to life can be sealed. The book ends on that separation, the couple lost in the abyss and the ship racing to reach the Doors before it is too late.