Mum’s the word on a tautologically titled episode of Star Trek: Discovery.

*SPOILERS*

After the tawdry torture porn of last week’s denouement, “Perpetual Infinity” opens with a flashback to Burnham’s happy childhood where this exceptionally gifted and inquisitive child was apparently completely oblivious to her parents’ line of work in their secret laboratory home. But it turns out it’s only a near-death experience for Burnham as she wakes in sickbay – and Culber’s back on duty. I guess after being brought back from the dead by extra-dimensional mushrooms, having a fist-fight with your own murderer and breaking up with your husband, a five-minute session with an ex-counsellor is all it needs to get your job back.

Meanwhile, on the Section 31 ship, we pick up with Leland, who’s under the influence of the rogue AI Control – who’s having fun appearing as various people a la The First from “Buffy The Vampire Slayer” before going the full assimilation and taking Leland over with an injection of nanites. For a season which has, so far, been all about referencing “Star Trek: The Original Series”, could it be that “Star Trek: Discovery” has actually been sneakily telling us the origin story of The Next Generation ’s most famous foes: the Borg? Then again, maybe not, because the Borg were big on assimilation and hardly ever tried to disembowel their opponents. Poor old Tyler, back to sickbay again. Good job he’s on excellent terms with Discovery‘s recently reinstated Doctor.

After last week’s muddled mish-mash seemed to fritter away the good work the season has built up, “Perpetual Infinity” – namechecked during the episode in a moment so clumsy it’s only surpassed by last week’s ‘time crystal’ goofiness – does a pretty good job of tightening things up again. While Burnham’s mother has clearly suffered – it sounds like she probably had to sit through the whole of “Star Trek: Discovery” season 1 for example – she’s bounced around the timeline so much she’s basically River Song at this point.

Driven by a determination to thwart the AI’s plans for universal genocide, she begs Pike to destroy the database of the MacGuffin sphere’s memories as they are the key to Control’s ultimate victory. It’s a sound plan which, surprisingly, takes very little convincing to bring the Discovery crew on side with but it’s not that easy: the sphere’s memory is unwilling to let itself be deleted, like a teenage boy’s worst browser history nightmare.

Thwarted by the most straightforward option (which would also have neatly explained the sphere’s knowledge’s absence in the future Trek series), the crew resort to good old fashioned technobabble, a plan of such linguistic complexity that it recalls the heady days of Geordi La Forge pounding his fist into his hand with excitement. Basically, they’ll download the sphere into the Red Angel suit and send it on a one way trip into the future where, if Control can get to it, it’ll be too late (it does conveniently overlook the fact that if Control can get to the massive technological database in the future, it’s contained in a self-sustaining time machine suit) and, as a bonus, they can sprinkle some magical plot dark matter particles onto the transport pattern enhancers and beam Burnham’s mum out of the timeloop she’s trapped in. The only problem is: Locutus of Leland is listening and asks Geogriou to help him syphon of the data download for Section 31.

Aside from a few irritating details (I find it hard to believe an organisation as paranoid and suspicious as Section 31 doesn’t routinely check its staff for contaminants in case they’ve been compromised), “Perpetual Infinity” finds strength in perpetual motion, as it powers the story forward without ever really pausing for breath. In many ways, it feels like a season finale right up until the moment when, in the middle of the climactic final battle, all parties start conspicuously pulling their punches in order to string the fight out for the remaining three episodes. Not that I’m complaining, because if the next three episodes are anything like this, we’re in for a barnstorming finale that’ll erase the sour taste of last year’s limp denouement completely.

Although my prediction that Burnham was The Red Angel seems to have been debunked, there’s a tantalising mention that the suit is DNA hard-coded and, given the number of times the similarity between Burnham’s genome and her mother has been mentioned, I’m pretty sure it’s foreshadowing that Burnham will definitely put on the Red Angel suit at some point before all is said and done. After all, Burnham’s mother knew nothing of the seven simultaneous signals, so someone has to send them…