Harp of Kings begins with a sister and brother arriving on Swan Island to compete for permanent places among the island's team of elite warriors and covert operatives. Over a lengthy training period, Liobhan and Brocc will not only be assessed against each other, they will need to prove themselves against the sons of chieftains and war-leaders. The competition is fierce; only two or three out of the twenty trainees will be chosen.
Liobhan knows she has what it takes, and as the only woman among the twenty, she's determined to prove she can be the best. Even if her fellow trainee Dau, a young nobleman, thinks she should stick to singing and playing the whistle — she's good at both — and forget about fighting. But when the opportunity comes for Liobhan to demonstrate what she is made of, it's in an unexpected and challenging form. The tests and trials that lie ahead take Liobhan and Brocc far from the island, and pit them against forces both human and uncanny.