Derwyddon, Y: Y Maen Rhial

Mae taith y derwydd Gwynlan yn parhau wrth iddo deithio o Ynys Môn i ynysoedd Heledd ac i Lychlyn er mwyn ceisio adfer y Maen Rhial ar ran pobl y Prydyn, ond a fydd ef a'i gyd-deithwyr yn medru goresgyn peryglon marwol cyn i'w hymchwil ddod i ben?

The druid sleuth Gwynlan continues on his journey from the isle of Anglesey to the Hebrides and to Scandinavia where he hopes to restore the Rhial stone, but will he and his co-travellers overcome life-threatening dangers before their quest comes to an end?