On the mystical island of Bardia, Bell Asbury’s sister is dying. A girl with an extraordinary but volatile gift for fusing magical elixirs, Bell was eleven when she accidentally struck her sister, Roza, with a magic that left her with an incurable illness. Six years later, she overhears her sister’s fiancé buying illicit ingredients for a brainwashing elixir. Alarmed and infuriated, Bell tries to end the engagement, but Roza's fiancé is from a noble house, the sisters’ father is in debt, and their mother is eager to have a connection to a powerful family.
Desperate to find a cure for Roza’s disease and an antidote to the brainwashing elixir, Bell uncovers a tangled web of secrets that leads to a man called the Seller of Secrets and his plot to use the brainwashing elixir to force the entire island to obey him. Bell alone can create an antidote, but her experiments risk the sanity of those she loves.
Rian, an infuriatingly handsome spy, offers to help her defeat the Seller of Secrets. Although she knows Rian is a master of deception, Bell can’t stop herself from falling for him. But with so many secrets coming to light, Bell doesn’t know who she can trust and who is working to control her gift.