Gaius Petrius Ruso is a doctor with the Twentieth Legion based in Deva (Chester) at the beginning of the reign of the new emperor Publius Aelius and his general Hadrianus. Ruso is also new to his job and is adjusting to the discomforts of a wet and cold Britain. He reluctantly acquires a reputation for investigating¬ unusual deaths and his battle experience often enables him to determine what has happened to the unfortunate victims.

Permanently short of money, largely because of the extravagances of his widowed stepmother, he consequently takes on some dangerous and foolhardy tasks and becomes involved in the affairs of the local disreputable bar. He also acquires a slave girl whom he has rescued from a violent and unsavoury owner. The Administrator, who is more concerned with finances and order than with the provision of good health care, causes Ruso many headaches but, ultimately, Ruso has the upper hand.