Here’s our spoiler-filled look at Star Trek Discovery’s fifth instalment.

While working hard to establish the show’s place in the wider Trek oeuvre, and a far less discretely episodic storytelling format than its fans are used to, Discovery spent much of ‘Choose Your Pain’ dipping into the original series lore in pleasing ways.

We’ve known for a while that the series would feature Harry Mudd (Harcourt Fenton Mudd in more formal circumstances) the twirly moustache-touting rogue first seen in the 1966 Original Series episode, ‘Mudd’s Women’ (S1E3) and then latterly in 67’s ‘I, Mudd’ (S2E12) and animated series episode ‘Mudd’s Passion’ – here played in a much more down to earth, far angrier and disheveled manner by Rainn Wilson.

His turn provides a geeky bit of backstory for the character, including a nod to his eventual wife, Stella, who also turned up in TOS, well… at least in android form. Rainn is due to appear in four more forthcoming episodes, so expect more of his cutting assessments of Federation expansionism and duplicitous dealings. Based on this outing, we look forward to them.

As was hinted by last week’s preview, Mudd turns up as long-term resident of the Klingon prison ship run by L’Rell, which has captured Discovery’s captain. Her presence there is one of several indicators of an ellipsis of time between this episode and the events of last week’s episode – more explicitly, we’re told that it’s been three weeks since Discovery’s intervention at Corvan II, and thus the last episode.

L’Rell’s quick rise to the captain of a completely new ship is a hint that there’s more going on than is immediately obvious. In fact, L’Rell presence at all is a conundrum. So much so, that I assumed I was looking at a different Klingon when she first appeared.

The last time we saw her, of course, she was aboard the abandoned remains of the Shenzhou with Voq offering to ally him to the house of Mokai. Three in-show weeks later, she’s running a prison ship and traumatising Star Fleet Lieutenants by ’taking a shine to them’.

Presumably, this means she has more of the house Mokai’s tendency to be “the deceivers, the weavers of lies” than we may have suspected – and could possibly be the main antagonist in the show going forward. She’s got a plan, that one, mark my words.

Think about it… If you were wondering how she could possibly be the Captain of that ship, and how to reconcile the problems Ash’s explanation of how he survived for seven months aboard it creates with the show’s stated time-line, you’re not alone. There’s almost certainly more to the ‘fortuitous’ meeting between Mudd, Ash, and Lorca than has been revealed this week – and more than Harry Mudd was letting on regarding how he got on the ship and ended up as a Klingon spy.

Other big questions are: what was the strategy of which L’Rell spoke aboard the Shenzhou, where’s Voq, and what exactly did L’Rell mean when she said he’d have to ‘sacrifice everything’? I’d wager Voq’s closer to all the action here than we may know right now. That would be speculation, though.

In a not-unrelated point: Ash is a pretty secondhand sci-fi name, isn’t it? Interesting choice, that.   

Let’s park any possible big reveals, though, and talk about what was the big shock of this episode; apart from Saru becoming a bit of a badass in the big chair.

Though heartwarming, and – yet again – reassuringly Trek-y, ‘Choose Your Pain’ was short on really high drama. That was until we got the final image of Lt. Stamet’s reflection lingering in the mirror long after what we interpret to be the physical incarnation of the man had left the room.

This, of course, riffs on another TOS classic creation, Star Trek’s mirror universe, a dystopian version of the prime timeline that appears to have diverged from the Trek-verse we know at the point where Vulcan’s first visit earth and they are greeted by Zephram Cochran’s blaster, rather than the more formal welcome we see in First Contact.

Again, we’ve known for a while that the mirror universe will feature in Discovery, but this is the first hint that it is somehow woven into the tale of the spore drive. It may even be the reason the seemingly game-changing technology is not Star Fleet standard in the show’s future – though there’s plenty of time for other things to get in the way.

It looks like next week could feature more callbacks to TOS, with the episode title – ‘Lethe’ – hinting back to a character in ‘Dagger Of The Mind’, from that show’s first season, which gave us a first look at the Vulcan mind meld. Lethe (played by Susan Wasson), fans may remember, was a resident of Tantalus V, a colony for the criminally insane who is a victim of the treatments used there. A minor plot point of ‘Dagger of the Mind’ is that Lethe was no-longer aware, or was coy about revealing, what crime had earned her a place on the planet – only that she was “malignant, hateful”. This means we could be about to find out what she did that was so bad.

Anyway, back to this week’s episode. It was another classy instalment of the wider Discovery arc, that continued the themes set up last week while diverging and setting up a whole new level of drama. Mudd promises to be an interesting addition to the show – along with his alternative political angle on the conflict between Klingons and the Federation, there’s always space for a not-unlikeable, largely amoral, rogue. One hopes the script, and Rainn Wilson’s performance taps into the traditional Harry Mudd vein in that sense.

‘Choose Your Pain’ also offered nice character moments for Stamets, Burnham, Tilly and Culber, though they largely took a back seat in terms of the action, which was left to Lorca, Ash and – pleasingly – Saru, who is coming to life wonderfully thanks to the great performance of Doug Jones. It also seems that the spore drive may be taking a back seat for a while, which will be interesting. With the fate of the Tardigrade decided (aw, they set it free), and the technology grounded for now, we may get a chance to explore more characters and discreet stories before we come back to the main arc full on.