Is there a murderous poltergeist on the loose?When an Oxford caretaker is killed by a fall down the library stairs, and a professor attacked, rumors fly that it's the work of a poltergeist who's been causing havoc at the college. The prof is a knitter, and a customer at Lucy Swift's shop, Cardinal Woolsey's. But Lucy thinks a very human killer is shifting the blame onto a ghost who can't defend themselves and she's determined to trap the real...