S01E04: 'The Poisoned Chalice'

It's taken a month, but finally Merlin manages to cast a wonderful spell on the audience with this adventurous and imaginative episode. Killer spiders, a seductive Big Bad and Merlin in a coma - it's serious.

The presence of Nimueh, played superbly by the delectable Michelle Ryan, adds a great deal to the story and provides a powerful antagonist - especially compared to the leaden CGI and Two Pints Of Lager baddies in previous weeks. The chameleon qualities in the character are convincingly brought out, with Nimueh able to look innocent and vulnerable in order to seduce various men, while a moment later she'll believably break out in a deliciously evil grin as she observes her prey suffering.

Nimueh's sly manipulation of Merlin is well realised, with Ryan and Colin Morgan really clicking together. There's more chemistry between them in their first brief meeting, when Nimueh poses as a handmaiden, than the entire month's worth of forced flirtation between Merlin and Guinevere. A nice role reversal also takes place in the relationship between Arthur and Merlin, with the master embarking on a mission to save his servant.

Arthur's quest to find the life-saving flower has a pleasing epic feel that's been sorely lacking in the series beforehand, although this part of the plot does bear an uncanny resemblance to the final episode of 1984 Doctor Who story 'The Caves Of Androzani'. Geekery aside, Arthur's journey benefits from the visual atmosphere in the mist-laden forest and the hordes of critters that descend on him under Nimueh's command inside the cave.

Poor direction and editing doesn't do the CGI monsters any favours, particularly in the woods. The creation is simply too exposed and would clearly benefit from the use of a real animatronic model to give it some genuine presence, rather than the cheap, fake look it bears.

Problems also emerge with the character of King Uther. No, he's not been computer generated too, but instead his ordering of Merlin to drink the suspected poison was a very, very callous act to a benevolent young man who had previously saved his son's life. There's no coming back from that for a long while, and it feels inconsistent with the stubborn yet sympathetic portrayal of Uther in recent weeks.

Overall though, a well-written and portrayed villain and a broader sense of adventure and invention ensure that this is comfortably the best Merlin to date. "Very good," observes Nimueh when the ledgehanging Arthur dispatches a monstrous arachnid with his sword. The same praise certainly applies to this episode.

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