The thing about detention is, it’s not a new lesson. It’s not part of the curriculum, so it’s not about picking up new information. It tends, if you get caught in it, to be about going over old ground and hopefully, if you’re doing it right, coming to a new and better understanding of things you already knew.

So it proves in Detained, Class’ bottle episode – and an opportunity to step back from what’s been happening thus far and take stock, before we head into the finale (but not before we learn what Miss Quill got up to after locking the kids in the classroom, that is; typical of Patrick Ness to play with the format of an eight episode series at the same time as appearing to do the obvious thing).

The plot itself was something fairly familiar, although nicely rendered. In fact, it had a touch of Paul Cornell’s Timewyrm: Revelation about it, as well as a hint of Russell T Davies’ Midnight (and many other things; it was pretty “classic” sci-fi), but the touches Ness added of his own worked very well. Taking the prison / classroom out of time and space was a spectacular moment in the instant it occurred, and then it was amusing watching the characters trying to work out what had happened. The rationale for all of this could have been presented as a cliché, but given that Ness’ concentration was, as always, on the principals and their development and relationships, anything previous about the situation seemed incidental.

So, what we had was an opportunity for each of our five teenagers to consolidate and confirm their purpose within the fiction. We saw Ram’s passionate side and learned why it’s both what sets him free and holds him back; we saw how April becomes the one who controls through her reticence. We saw how Tanya is concomitantly both the most hesitant and the most outspoken, and we saw Matteusz being strong by being flexible. And we saw Charlie, the one who has lost everything and owns everything, and around whom all of these other worlds orbit, despite being the least likely to induce those gravitational shifts. If what came in between was occasionally unintentionally awkward, the bouts of dialogue were electric. And Charlie’s arm in the door was stunning in its simplicity.

Funnily enough, given how Miss Quill has become something of an “in” character for adult viewers – and very much the one you can’t take your eyes off in any situation – Detained proved it far less of a risk in taking her out of the episode almost entirely than it might have been. The five “children” easily held the screen, the actors confirming their capabilities as well as the bond they share very readily. Katherine Kelly would simply have been intruding on their effectiveness, undermining their capacity to carry an episode by themselves. Plus, it looks like we’ll see plenty of Kelly next week, in what might be a barnstorming change of pace before the finale.

Class isn’t dealing in originality, but then there’s so little these days that’s truly unique. But what Patrick Ness is doing is taking a set of well-worn ingredients and creating a dish that for a certain generation will be both nourishing and diverting. For everybody else, there should enough there to make the experience worthwhile – but I guess for some the flavours will just never be acceptable. Detained was a small-scale episode that delivered on everything it modestly promised, and left a satisfying taste in the mouth. That was the aperitif, next week the sorbet and then – well, we’ll see.