When a heartbroken Welsh warrior appears to Hecate seeking assistance she sees it as her duty to help. As her friendship with the glassworker Gil Wheatley deepens, she understands the suffering of the lovelorn spirit. However, the arrival of a new master of the library throws her position into doubt, and may mean she must leave the library. Meanwhile, a savage murderer is terrorising the city. When a second killing shows similarities, Inspector Winter suspects something supernatural at work and calls on Hecate for her help.

With Hecate’s place in the cathedral no longer secure, her best friend soon to be wed, and a growing relationship, everything in Hecate’s life seems in a state of flux. She must put aside her own personal concerns however, if she is to fulfil her promise to the Welsh nobleman, and succeed in stopping the murderous progress of the vengeful phantom.