Book 3 of the Altered Destinies Series.
Colton Reynolds is still the son of Ares, but what if Kayla Knowles was a daughter of Poseidon and Percy Jackson's half sister, yet still was good at archery? How would this play out since it means Colton gets dragged into some (but not all) of Percy's antics?
And why does Kronos seem to not want to leave Colton's head?