Guinevere Jones S02E11 - What Guinevere Knew

Intent on saving Merlin, Gwen enters Faerie and succeeds in going back to Merlin's time. Tapping into her former life as Guinevere, she remembers the secret of how to find Merlin's Stone. Gwen manages to rescue Merlin and, thwarting Morgana's attempt to capture the crystal, returns to the 21st century with the crystal to save Karen - with O'Leary in hot pursuit.