In the last years of the Viking Era, priestess Astrid takes on the task of recording the True Things. A skáldmær learning to write royal sagas and a member of one of the last remaining temples to the Goddess Nerthus, Astrid knows she must protect her secrets from the bishops of the Roman Church and from Norway's kings – a task that becomes harder when she falls in love. Orphaned Mercy is taken from the Glasgow Poorhouse by a man with ill intentions. When she realises the true horror of his evil plans, she escapes to London. She is fortunate to meet Ann Radcliffe, a successful yet reclusive author of Gothic horror novels. Mercy joins Ann's household and is taught storytelling. But even though she's finally found a home, she longs to discover her true identity. Mia is given the ancient book Systir Saga at the funeral of her cousin. With her best friend, Cait, she travels from the Blue Mountains to the UK on a quest to decipher the runes and learn more about her mysterious heritage. They journey to an ancient rock mound on a windswept island in the Orkneys. There, Mia seeks to unearth the secrets of the Systir Saga.