In an alley near Meriwether Prep, Annabeth pulls Percy and Tyson away from the burning school and immediately reacts with alarm to Tyson. Percy is glad to see Annabeth, but he is upset by her hostility toward Tyson after Tyson has just saved his life. Annabeth identifies the attackers in the gym as Laistrygonians, giant cannibals, and says the deeper problem is not the police but urgent trouble at Camp Half-Blood. When Percy mentions his dream about Grover, Annabeth reveals she has instead been sensing danger at camp and says monsters have been chasing her from Virginia.

Percy explains to Tyson that Greek gods are real and that Percy and Annabeth are half-bloods who attract monsters. Tyson accepts the explanation with surprising ease and focuses on Percy being the son of Poseidon, which unsettles Percy because Tyson does not react like a normal mortal. Percy decides Tyson cannot be abandoned, despite Annabeth's obvious discomfort, so the three of them sneak through the city together while the school fire grows behind them.

On a street corner, Percy notices how worn and injured Annabeth looks, confirming that her trip has been dangerous. Annabeth uses a drachma and an Ancient Greek summons to call the Gray Sisters' taxi, a smoky supernatural cab. The driver initially refuses to take Tyson, but Annabeth offers extra pay and gets all three aboard. Percy then discovers that the cab is run by the three Gray Sisters—Wasp, Anger, and Tempest—who are blind except for a single shared eye and who also fight over a single tooth.

The ride becomes chaotic and dangerous as the sisters drive wildly through New York while bickering, trading the eye, and nearly crashing. Annabeth insists the Gray Sisters are wise and the fastest route to camp, but Percy is unconvinced, especially when Tyson becomes violently carsick. In the middle of the argument, one sister blurts out that they know "the location you seek," hinting that they possess important knowledge Percy has not yet asked for.

When the shared eye is knocked into the backseat, Percy grabs it with a piece of his shirt and refuses to return it until the sisters explain themselves. As the taxi accelerates at impossible speed across Long Island, Percy threatens to throw the eye away unless they speak. The Gray Sisters finally shout a cryptic clue—"30, 31, 75, 12"—and Percy gives the eye back so they can stop the cab and reach their destination safely.

The taxi screeches to a halt at the base of Half-Blood Hill, and Tyson recovers just in time to get out. Percy demands an explanation of the numbers, but Annabeth cuts him off because a new emergency is already visible. Looking up the hill, Percy sees a group of campers under attack, confirming that the danger at Camp Half-Blood is immediate and real.