Percy races from the Natural History Museum to the Air and Space Museum, removing Annabeth’s invisibility cap once inside. He crashes into Thalia and finds Grover, Zoë, and Bianca; Zoë is furious that Percy followed the quest, but Percy urgently reports that Luke, Dr. Thorn, the General, and twelve skeleton warriors are nearby.

The warning unsettles the group. Grover explains that Artemis’s trail seemed to lead to the museum because of a powerful monster scent. Zoë refuses to believe Percy saw the General, but the danger of the skeleton warriors forces the group to consider leaving. Tension rises when Zoë insists Percy is not part of the quest and Thalia defends taking him along.

Before the argument can continue, the Nemean Lion attacks inside the museum. Zoë and Bianca’s arrows bounce off its metallic fur, Percy’s sword cannot cut it, and Thalia holds it back temporarily with Aegis. Percy realizes the lion’s mouth is its only vulnerable spot, but the monster moves too fast and keeps its mouth guarded.

Percy spots the gift shop and remembers the awful space food sold there. While Thalia distracts the lion, Percy gathers freeze-dried snacks, then throws them into the lion’s mouth to make it gag and roar. When Percy forces the lion’s jaws open, Zoë and Bianca shoot arrows into its mouth and kill it.

As alarms sound and museum visitors flee, the lion dissolves and leaves behind its pelt, which Zoë says belongs to Percy as a spoil of war. The pelt transforms into a golden-brown duster. Grover briefly confuses the security guards with a song, but Zoë points out the greater threat: gray-clad skeleton warriors crossing the lawn toward them.

Percy offers to draw the skeletons away because they are hunting his scent, but Zoë refuses to abandon him. Though reluctant, Zoë accepts that fate has made Percy the fifth quest member, and the group prepares to leave together.