Bradfield is in panic as someone preys on its most vulnerable—its hospital patients. Carol must juggle how to warn the public, and how to keep a predatory MI5 official at bay. The only way out is to solve the case fast—but there is very little to go on, even for Tony.

Tony and Carol think they've scored early when two murders lead to one man. The trouble is that the man is in prison; could he really be controlling it all from the inside?

Tony and Carol investigate when a 500-year-old skeleton in unearthed while foundations are being excavated for a hotel extension. However, underneath the body, they find two more modern corpses. And when a journalist vanishes, and the hotel is burnt to the ground, Tony suspects the suspect may be obsessed with Joan of Arc and killing imagined heretics.

Tony finds his work with the police compromised when a student from his university is abducted. But that's not his only worry—Carol stops trusting him when he allows one of his own pupils to help with the investigation.