It is October 1477 and Roger the Chapman, still basking in wedded bliss, is surprised to find himself feeling restless again. He is driven towards Plymouth, certain that he is needed there, and on his arrival is confronted by the brutal murder of a wealthy old man, Master Capstick. The chief suspect, Capstick s great-nephew Beric, has completely vanished and local gossip is rife with the rumour that he has eaten the Saint John s fern which can make a man invisible. Roger begins his own enquiries, an action which provokes an attempt on his life and he realises that he is close to a truth that is even more extraordinary than the superstition...