Radiant Sin (Dark Olympus #4)

As a disgraced member of a fallen house, Cassandra Gataki has seen firsthand what comes from trusting the venomous Thirteen. But when the maddeningly gorgeous and kind Apollo asks her to go undercover as his plus-one at a week-long party hosted by a dangerous new power player…Cassandra reluctantly agrees to have his back.

Radiant Sin is book number 4 in the Dark Olympus series by Katee Robert.