Katarina’s death is a bit of a shocker.  The last few episodes have suggested that she’s now firmly a regular, so her sudden demise (sucked out of the airlock with Kirksen) certainly helps to reinforce the impression that the stakes in this story are higher than usual (as we’ll see, other allies will also perish before we reach episode twelve).

But the nature of this type of adventure serial means that it’s impossible to dwell on her fate for too long.  Steven sounds upset and the Doctor delivers a nice little tribute (“She didn’t understand. She couldn’t understand. She wanted to save our lives and perhaps the lives of all the other beings of the Solar System. I hope she’s found her Perfection. Oh, how I shall always remember her as one of the Daughters of the Gods. Yes, as one of the Daughters of the Gods”) but once that’s done they press on and she’s only mentioned again at the end of the final episode as Steven counts the human cost of their victory.

Although the story seems set to be a re-run of The Chase (the Dalek pursuit ship wasn’t able to intercept the Doctor on Desperus, so you assume it’ll carry on following them) at present it takes a different tack.  The Black Dalek orders the pursuit ship to be destroyed as he doesn’t tolerate failure (another sign that the Daleks are back to their ruthless, single-minded best) and then contacts Chen – telling him that he’ll be the one to regain the core and exterminate the Doctor and his friends.  This is another sign that the Daleks are thinking – it would have been impossible for them to travel to Earth and not attract attention, so using their human agents is the logical course of action.

Every good megalomaniac needs a confidant and Chen has Karlton (Maurice Browning).  Browning is wonderfully smooth and his performance gives us the impression that Karlton is well aware of his worth.  It’s a pity that he doesn’t stick around longer as he would have served as a good sounding board for Chen’s various plots and dreams.

The Traitors has an increasing vice-like feel, as the Doctor, Steven and Bret (now back on Earth) find it difficult to know who they can trust.  Bret contacts Daxtar (Roger Avon) but he’s part of the conspiracy and Bret shoots him dead.  The Doctor is appalled by this, but as he was powerless to intercede it’s another sign that the Doctor isn’t in control – at present he’s being buffeted along by events whilst others (both enemies and allies) hold the upper hand.

This episode introduces us to Sara Kingdom (Jean Marsh).  Chen initially refers to her by her surname and sums up her character.  “Ruthless, hard, efficient. And does exactly as ordered.”  This scene is another mis-direct, as no doubt the audience is supposed to be surprised when this top agent is revealed not to be a man but a woman.  Sara, like the troopers later seen in Blakes 7, is a product of her training.  Once she has her orders then she’ll carry them out without question.  It’s not difficult to imagine that Terry Nation was again drawing on his memories of WW2 when crafting this character.

If Katarina’s death at the start of this episode was a jolt, then so is Bret’s demise at the end.  He’s shot dead by Sara which spells trouble for the Doctor and Steven as she’ll now be gunning for them …..