After the drama of her imprisonment in The Dark Tower last week, plus the untimely death of her impetuous brother Sir Elyan, it is no wonder the Queen appears to be a little out of sorts. It is also the perfect cover for some devilishly evil doings. Of course, we the audience know perfectly well that Gwen is under the influence of Morgana but that remains a secret not shared with the rest of Camelot.

The episode begins with a bang in the form of an assassination attempt leaving our would-be killer Queen on the back foot. As Gwen swiftly implements a plan B, which involves the setting up of an innocent stable hand, she does not reckon for detective Merlin on the case.

This is another great episode for Angel Coulby who demonstrates new facets to Gwen’s character, which range from the over-wrought wife to cold-blooded killer as she serves up a sweet blend of scheming evil. There are shocking moments in store when Gwen moves beyond vengeful to frankly murderous, and yet somehow we forgive her because she is really rather good at it! The performance at the King’s bedside for Sir Leon is utterly sublime, reeling him in and gaining his total support.

It is not all about Gwen thought, as Merlin’s instincts put him on the trail soon enough. When the stakes are raised, he finds himself in hot water and struggling to keep up with this new threat. The story becomes a complex game of cat and mouse as Gwen attempts outmanoeuvre him, both seemingly aware of what the other is up to.

With this new agent of chaos on the inside, we see less of Morgana this week than last though she does have a background role, lurking on the outskirts of the citadel and later entering in disguise. Gaius gets a good showing too and the Kinghts are well used here as the story plays out mostly within the Camelot’s walls.

For more direct comedy, there is a welcome return for the Camelot cook Audrey (Zee Asha) who finds herself receiving some home truths about the state of her dumplings when she accosts Merlin in his disguise of Dragoon the Great.

This episode is quite the most fun the cast of Merlin have had so far this year. From evil Gwen to detective Merlin, the cast are clearly having a ball playing with this altered dynamic.

Despite the murderous shenanigans, returning director Alice Troughton treads the line perfectly between comedy and drama. The whole episode plays out as a wonderful light relief after last week’s drama, but yet somehow never feels insubstantial either. A mid-series treat!

[★★★★☆]