Gwen and Elyan are paying respects to their late father, but their journey back to Camelot ends in tragedy with an ambush that leaves the Knights wounded and poor Gwen kidnapped by Morgana (who else?) Morgana imprisons her in the Dark Tower, a place said to contain the mind’s deepest fears. Arthur, of course, wastes little time mounting a rescue mission, but it’s far from an easy task requiring a journey through perilous lands.

If this episode’s plot sounds like classic fairy tale territory then you wouldn’t be far wrong. Although, for the most part, this is probably the darkest episode of Series 5 yet, topping The Death Song of Uther Pendragon. It’s certainly pushing the boundaries of the pre-watershed audience.

Half the plot follows Merlin, Arthur and the Knights and their treacherous trek. A bulk of the time is spent at “The Impenetrable Forest”, a place where Merlin meets a magical being called Queen Mab (Kelly Wenham). She certainly gives the Great Dragon a run for his money in the riddle stakes and is a fun addition to the world. The Knights eventually reach the titular Dark Tower, which itself is laden with traps. Some of which have lasting consequences for the gang.

Naturally with Gwen’s kidnapping having a profound effect on everyone, there’s less humour than usual. Gwaine is the only one who really provides any light relief this week. The usual back and forth banter between Merlin and Arthur is toned down. With so much on the line, Merlin really gets to take charge and Arthur places his trust in Merlin almost without question. Elyan also gets a slightly expanded role.

The other half of the story focusses on Gwen and Morgana, and this is by far more interesting part of the episode. There are some brilliantly creepy moments as the episode dips into the realm of psychological horror. Trapped in a pitch black room surrounded by nothing but screams and evil apparitions of familiar faces, Gwen’s torment is superbly directed. Her mental breakdown at Morgana’s hand gives Angel Coulby her most screen time this series and consequently her best material yet.

While this could have been a tired Morgana plot, her plan here is actually far cleverer than it appears on the surface, with the extent of this only realised in the closing moments. Katie McGrath gets to play two sides of the character as she flips between good and evil. It’s strange seeing her trying to play nice with Gwen, and you are never quite sure what is going on.

Overall, this is a great installment. If you liked the Merlin quest-type episodes from past series, then you will love this episode.  It all ends on a sombre note and not everything is wrapped up, with some major implications for the rest of the series.

9/10