Travelling through Time Doors is forbidden. Absolutely. Both Ways. No young person is supposed to travel in Time from present-day Wales to old-time Ynys Haf; no young person is to travel from Ynys Haf to Wales - to the quiet little village of Blaengwynfi, for example. Why not? Because Great Merlin has forbidden this dangerous time-travel, that's why not. Trouble is, there are some young persons - very disobedient or very adventurous ones, depending on how you look at it - who seem willing to risk it. Forbidden lands, strange creatures, magic on every corner...Betsan's Mam doesn't call her Betsan the Brave for nothing, does she?