Merlin - Series 3 - Love in the Time of Dragons

When an old flame of Gaius's arrives in Camelot, Merlin is pleased to see a different side to his curmudgeonly mentor. But after discovering she is under the influence of a Manticore, a creature from the Old Religion, Merlin has no choice but to tell his old friend of Alice's evil intentions. Blinded by love, the old physician refuses to believe Merlin's story, and the two friends fall out. With the King in danger and all signs pointing to Alice and her evil pet, Merlin must somehow make Gaius come to his senses before it is too late.