The Saint John's fern - Kate Sedley

It is October 1477 and Roger the Chapman, still basking in wedded bliss, is surprised to find himself feeling restless again. He soon sets off on his travels, driven south by the feeling he is needed there. Roger eventually arrives in Plymouth to be confronted by the brutal murder of a wealthy old man, Master Capstick. The old man's great-nephew, Beric is widely believed to have committed the murder, but has vanish completely. Locals rumour suggests that Beric has eaten the Saint John's fern which can make a man invisible. Roger, quick to dismiss such old-fashioned beliefs, begins his own investigation and soon finds his life in danger. It appears that he is close to a truth that is even more extraordinary than the superstition...