So this is based on one of the short stories in Rick Riordan’s Demigod Files called Percy Jackson and the Bronze Dragon and is set between The Battle of the Labyrinth (book 4) and the Last Olympian (book 5).
It is set at Camp Half-Blood during a game of Capture the Flag where Poseidon and Hephaestus are against Athena and Aphrodite. Annabeth and Selina capture Percy, which puts Beckendorf in danger. The general gist is that they find some gigantic, deadly ants dragging a Bronze Dragon head, and Annabeth has to activate it to save Beckendorf. In the end, they go back, expecting Capture the Flag to be long over, but it is still going….
Percy, Annabeth, Selina and Beckendorf go back after their adventure in the woods, involving a Bronze Dragon and some very big, very dangerous ants, expecting Capture the Flag to be over. But it is still going, and Annabeth’s siblings run into them and take Percy and Beckendorf prisoners as they are on the opposite team.