We are used to spies tailing one another; keeping out of sight of their target – though passers by can see them, they just see another pedestrian – it’s only the target that matters. There’s something incredibly spooky about Steed wandering through the streets with a tail quite literally stepping on his heels – someone who can stand right in front of him and not be seen.

There’s also the repeating pattern – a bit like in The Hour That Never Was (another hypnosis episode) – starting out as a light hearted routine and growing more and more sinister (just as the story seemed unpromising at the start, but grew in my estimation as it became darker). There are some iffy choices – Steed is uncharacteristically caught off guard at the beginning, which makes it less obvious that when he’s flattened later it’s because he cannot see his assailant and not just because he’s lost his edge. And though there some night time location shots are a welcome change, there are also some unconvincing studio scenes.

Mother is replaced for most of this episode by Father – a blind woman – who is both better written and a more credible spy master. She has textured paintings – and though the sets are nowhere near as impressive, it reminded me a little of Second Sight. Unfortunately, Mother returns towards the end of the episode. What a contrast! “If we can’t trust you, who can we trust” he tells Steed, completely recklessly – compare this to Father instantly downgrading Steed’s security status and having him followed. Had he been assassinated, he’d have only had himself to blame… (And I’d not have been mourning.)

But it is refreshing to see Steed, who has become almost invincible, show a little frailty as he begins to contemplate the frightening possibility that his mental health is failing.

We also get two renegade Time Lords in this one! The Master and The Rani together – perhaps the only time outside Mark of the Rain? But it’s not Ainlee, it’s Roger Delgado with Kate O’Mara.

Notes: Steed’s phone number is Whitehall 9819. Tara has two moose heads mounted on a fluorescent pink backboard in her flat – how had I not noticed that before? Ugh.

Surprised though I was to find myself enjoying the episode by the end, I still don’t really understand the title. Stay Tuned?