After her first mission for the Fair Seas Treaty Alliance, Intelligencer Dagrun Lund returns home to find that her twin sister Inger has disappeared.

Using all of her skills as well as her strong Trait, Dag stows away on a ship and follows her sister to Strongrock, an island that is home to pirates. On Strongrock, Dag discovers that the pirates are hiding dangerous secrets; secrets that threaten to ensnare Inger and turn her against her country and her twin.

When fellow Intelligencer Calder Rahmson arrives to escort Dag back home, the two of them find themselves targeted by the pirates. Fleeing for their lives, Calder and a heartbroken Dag are forced to leave Inger behind. Dag vows to find her sister and save her from the pirates, but when she discovers that the pirates are a threat to the Fair Seas Treaty Alliance, Dag faces a terrible choice between saving her sister and saving the Alliance.