Merlin: Season 1, Episode 8

1 - 8: The Beginning of the End

When the identities of a druid and his boy apprentice, Mordred, are discovered in Camelot, they are soon on the run from the guards, but when Merlin hears the boy's cry for help in his mind, he saves the boy. The druid ends up being executed, leaving the boy all on his own. Although the Great Dragon has told Merlin to be careful on who he meets, he still puts Arthur's life in danger keeping the boy safe. The Great Dragon tells Merlin that if he saves the boy Merlin can not fulfil his destiny - the young boy is going to kill Arthur.