We're now halfway through series 5 and "The Dark Tower" lost points for leaning so heavily on a storyline the fantasy genre (but more importantly this show) has tackled many times before. It's true that variations on slaying beasts, rescuing damsels, and going on quests for magical antiquities can't really be avoided in shows of this nature, but I always hope for fresh twists on old ideas. Instead, you tend to find that Merlin embraces all the obvious clichés and hopes doing them well is enough for audiences to forgive the lack of core creativity.
Queen Gwen (Angel Coulby) is kidnapped by Morgana (Katie McGrath) in the teaser, finding herself shackled inside the notorious Dark Tower—a place Arthur (Bradley James) later informs everyone is something of a ghost story every young knight is told, although the knights he imparts this information to don't seem to have heard the tales. Regardless, Arthur and his knights are joined by Merlin (Colin Morgan) on a dangerous mission to rescue the Queen from Morgana's clutches, but find it particularly hard going when they encounter the Impenetrable Forest—which plays games with their sense of direction. Games of another kind are being played on Gwen meanwhile, who discovers the Dark Tower is so-called because it messes with your mind. Disembodied screams, things dripping an oily substance from the ceiling, luminous phantoms of her friends toying with her emotions... it all becomes so unbearable that Gwen starts losing her marbles, and is particularly confused when Morgana appears to be the only person sympathising with her plight.
"The Dark Tower" was a great execution of tired ideas. It wasn't breaking new ground in the slightest, but series 5's given Merlin such an almighty boost in terms of production values it was nevertheless very enjoyable to watch. The scares Gwen encountered were rather distressing for a "family show" (although it's getting difficult to label Merlin with that tag, because I wouldn't show this episode to a child under eight), and I particularly loved the music used throughout this hour.
What didn't work for me was the conclusion of this hour, which offered us two huge developments that didn't really work. The first was the death of Sir Elyan (Adetomiwa Edun) after rescuing his sister from an enchanted sword, only to suffer a lethal blow. A potentially stirring moment, but one that utterly flopped because Merlin's done a very poor job developing Elyan's character (I'd almost forgotten he was part of the show), and an even worse job reminding us that he's actually Gwen's brother (this episode was even forced to open with a blunt reminder of that fact with Gwen and Elyan at their father's grave). Consequently, the death of Sir Elyan slipped by without managing to push the desire emotional buttons. A shame, but the writers only have themselves to blame—because the only knight who's been given any worthwhile writing is Sir Gwaine (Eoin Macken).
The second misstep was the big twist of the episode, with the rescued Gwen revealed to have been successfully brainwashed by Morgana into now helping her destroy Arthur. The idea's sound in theory, but it was frankly ridiculous for this massive change in Gwen's character/principles to occur in the space of just one episode. I don't expect Homeland levels of complexity with a storyline of this type on a show like Merlin, but absolutely nothing about it rang true to me. I can believe Morgana caused a psychological crack in Gwen after days of prolonged exposure to a haunted chamber, but to suddenly despise Arthur so much that she's going to help Morgana ruin her husband? Sorry, but no. Why would Gwen suddenly hate her husband and Camelot? What argument is there to convince her that Morgana's the wronged party? Why would she want to assist Morgana after everything she's done over the years? She was responsible for the death of her own brother just hours ago!
Unfortunately, while I can see the dramatic merit of putting Gwen in league with Morgana, it just wasn't plausible in the slightest. Maybe if there were a few genuine reasons for Gwen to dislike Arthur and his ideals, which Morgana could have seized upon and exploited with a clever argument, this whole idea may have worked brilliantly, but there wasn't. I'm sure many people won't care and will happily go along with this change, but if Merlin wants to be treated with greater respect the writing needs to get a lot smarter.